Debug engine hangs randomly (race condition)?

[zmbc]

With a notebook with a single cell that says:

import pandas as pd

for foo in ["bar", "baz"]:
    pd.DataFrame({'foo': [1, 1]}).merge(pd.DataFrame({'foo': [1, 1]}), how="left", on="foo", validate="1:1")

The command papermill ploomber_test.ipynb out.ipynb -k python3 --engine debug frequently (but not always) hangs indefinitely. When I ctrl+c it, I get:

Input Notebook:  ploomber_test.ipynb
Output Notebook: out.ipynb
Executing:   0%|                                                                                                                                                                                                                                                                       | 0/3 [00:00<?, ?cell/s]Executing notebook with kernel: python3
Executing:  33%|█████████████████████████████████████████████████████████████████████████████████████                                                                                                                                                                          | 1/3 [00:01<00:03,  1.94s/cell]Executing:  67%|██████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████                                                                                     | 2/3 [00:30<00:15, 15.37s/cell]

Aborted!
Task exception was never retrieved
future: <Task finished name='Task-8' coro=<PloomberNotebookClient.async_execute_cell() done, defined at ../.venv/lib/python3.11/site-packages/ploomber_engine/client.py:101> exception=CellExecutionError('An error occurred while executing the following cell:\n------------------\nimport pandas as pd\n\nfor foo in ["bar", "baz"]:\n    pd.DataFrame({\'foo\': [1, 1]}).merge(pd.DataFrame({\'foo\': [1, 1]}), how="left", on="foo", validate="1:1")\n------------------\n\n----- stdout -----\n> \x1b[0;32m../.venv/lib/python3.11/site-packages/pandas/core/reshape/merge.py\x1b[0m(1510)\x1b[0;36m_validate\x1b[0;34m()\x1b[0m\n\x1b[0;32m   1508 \x1b[0;31m        \x1b[0;32mif\x1b[0m \x1b[0mvalidate\x1b[0m \x1b[0;32min\x1b[0m \x1b[0;34m[\x1b[0m\x1b[0;34m"one_to_one"\x1b[0m\x1b[0;34m,\x1b[0m \x1b[0;34m"1:1"\x1b[0m\x1b[0;34m]\x1b[0m\x1b[0;34m:\x1b[0m\x1b[0;34m\x1b[0m\x1b[0;34m\x1b[0m\x1b[0m\n\x1b[0m\x1b[0;32m   1509 \x1b[0;31m            \x1b[0;32mif\x1b[0m \x1b[0;32mnot\x1b[0m \x1b[0mleft_unique\x1b[0m \x1b[0;32mand\x1b[0m \x1b[0;32mnot\x1b[0m \x1b[0mright_unique\x1b[0m\x1b[0;34m:\x1b[0m\x1b[0;34m\x1b[0m\x1b[0;34m\x1b[0m\x1b[0m\n\x1b[0m\x1b[0;32m-> 1510 \x1b[0;31m                raise MergeError(\n\x1b[0m\x1b[0;32m   1511 \x1b[0;31m                    \x1b[0;34m"Merge keys are not unique in either left "\x1b[0m\x1b[0;34m\x1b[0m\x1b[0;34m\x1b[0m\x1b[0m\n\x1b[0m\x1b[0;32m   1512 \x1b[0;31m                    \x1b[0;34m"or right dataset; not a one-to-one merge"\x1b[0m\x1b[0;34m\x1b[0m\x1b[0;34m\x1b[0m\x1b[0m\n\x1b[0m\n----- stdout -----\n--KeyboardInterrupt--\n\nKeyboardInterrupt: Interrupted by user\n------------------\n\n\x1b[0;31m---------------------------------------------------------------------------\x1b[0m\n\x1b[0;31mMergeError\x1b[0m                                Traceback (most recent call last)\nCell \x1b[0;32mIn[2], line 4\x1b[0m\n\x1b[1;32m      1\x1b[0m \x1b[38;5;28;01mimport\x1b[39;00m \x1b[38;5;21;01mpandas\x1b[39;00m \x1b[38;5;28;01mas\x1b[39;00m \x1b[38;5;21;01mpd\x1b[39;00m\n\x1b[1;32m      3\x1b[0m \x1b[38;5;28;01mfor\x1b[39;00m foo \x1b[38;5;129;01min\x1b[39;00m [\x1b[38;5;124m"\x1b[39m\x1b[38;5;124mbar\x1b[39m\x1b[38;5;124m"\x1b[39m, \x1b[38;5;124m"\x1b[39m\x1b[38;5;124mbaz\x1b[39m\x1b[38;5;124m"\x1b[39m]:\n\x1b[0;32m----> 4\x1b[0m     \x1b[43mpd\x1b[49m\x1b[38;5;241;43m.\x1b[39;49m\x1b[43mDataFrame\x1b[49m\x1b[43m(\x1b[49m\x1b[43m{\x1b[49m\x1b[38;5;124;43m\'\x1b[39;49m\x1b[38;5;124;43mfoo\x1b[39;49m\x1b[38;5;124;43m\'\x1b[39;49m\x1b[43m:\x1b[49m\x1b[43m \x1b[49m\x1b[43m[\x1b[49m\x1b[38;5;241;43m1\x1b[39;49m\x1b[43m,\x1b[49m\x1b[43m \x1b[49m\x1b[38;5;241;43m1\x1b[39;49m\x1b[43m]\x1b[49m\x1b[43m}\x1b[49m\x1b[43m)\x1b[49m\x1b[38;5;241;43m.\x1b[39;49m\x1b[43mmerge\x1b[49m\x1b[43m(\x1b[49m\x1b[43mpd\x1b[49m\x1b[38;5;241;43m.\x1b[39;49m\x1b[43mDataFrame\x1b[49m\x1b[43m(\x1b[49m\x1b[43m{\x1b[49m\x1b[38;5;124;43m\'\x1b[39;49m\x1b[38;5;124;43mfoo\x1b[39;49m\x1b[38;5;124;43m\'\x1b[39;49m\x1b[43m:\x1b[49m\x1b[43m \x1b[49m\x1b[43m[\x1b[49m\x1b[38;5;241;43m1\x1b[39;49m\x1b[43m,\x1b[49m\x1b[43m \x1b[49m\x1b[38;5;241;43m1\x1b[39;49m\x1b[43m]\x1b[49m\x1b[43m}\x1b[49m\x1b[43m)\x1b[49m\x1b[43m,\x1b[49m\x1b[43m \x1b[49m\x1b[43mhow\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[38;5;124;43m"\x1b[39;49m\x1b[38;5;124;43mleft\x1b[39;49m\x1b[38;5;124;43m"\x1b[39;49m\x1b[43m,\x1b[49m\x1b[43m \x1b[49m\x1b[43mon\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[38;5;124;43m"\x1b[39;49m\x1b[38;5;124;43mfoo\x1b[39;49m\x1b[38;5;124;43m"\x1b[39;49m\x1b[43m,\x1b[49m\x1b[43m \x1b[49m\x1b[43mvalidate\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[38;5;124;43m"\x1b[39;49m\x1b[38;5;124;43m1:1\x1b[39;49m\x1b[38;5;124;43m"\x1b[39;49m\x1b[43m)\x1b[49m\n\nFile \x1b[0;32m../.venv/lib/python3.11/site-packages/pandas/core/frame.py:10093\x1b[0m, in \x1b[0;36mDataFrame.merge\x1b[0;34m(self, right, how, on, left_on, right_on, left_index, right_index, sort, suffixes, copy, indicator, validate)\x1b[0m\n\x1b[1;32m  10074\x1b[0m \x1b[38;5;129m@Substitution\x1b[39m(\x1b[38;5;124m"\x1b[39m\x1b[38;5;124m"\x1b[39m)\n\x1b[1;32m  10075\x1b[0m \x1b[38;5;129m@Appender\x1b[39m(_merge_doc, indents\x1b[38;5;241m=\x1b[39m\x1b[38;5;241m2\x1b[39m)\n\x1b[1;32m  10076\x1b[0m \x1b[38;5;28;01mdef\x1b[39;00m \x1b[38;5;21mmerge\x1b[39m(\n\x1b[0;32m   (...)\x1b[0m\n\x1b[1;32m  10089\x1b[0m     validate: \x1b[38;5;28mstr\x1b[39m \x1b[38;5;241m|\x1b[39m \x1b[38;5;28;01mNone\x1b[39;00m \x1b[38;5;241m=\x1b[39m \x1b[38;5;28;01mNone\x1b[39;00m,\n\x1b[1;32m  10090\x1b[0m ) \x1b[38;5;241m-\x1b[39m\x1b[38;5;241m>\x1b[39m DataFrame:\n\x1b[1;32m  10091\x1b[0m     \x1b[38;5;28;01mfrom\x1b[39;00m \x1b[38;5;21;01mpandas\x1b[39;00m\x1b[38;5;21;01m.\x1b[39;00m\x1b[38;5;21;01mcore\x1b[39;00m\x1b[38;5;21;01m.\x1b[39;00m\x1b[38;5;21;01mreshape\x1b[39;00m\x1b[38;5;21;01m.\x1b[39;00m\x1b[38;5;21;01mmerge\x1b[39;00m \x1b[38;5;28;01mimport\x1b[39;00m merge\n\x1b[0;32m> 10093\x1b[0m     \x1b[38;5;28;01mreturn\x1b[39;00m \x1b[43mmerge\x1b[49m\x1b[43m(\x1b[49m\n\x1b[1;32m  10094\x1b[0m \x1b[43m        \x1b[49m\x1b[38;5;28;43mself\x1b[39;49m\x1b[43m,\x1b[49m\n\x1b[1;32m  10095\x1b[0m \x1b[43m        \x1b[49m\x1b[43mright\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m  10096\x1b[0m \x1b[43m        \x1b[49m\x1b[43mhow\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mhow\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m  10097\x1b[0m \x1b[43m        \x1b[49m\x1b[43mon\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mon\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m  10098\x1b[0m \x1b[43m        \x1b[49m\x1b[43mleft_on\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mleft_on\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m  10099\x1b[0m \x1b[43m        \x1b[49m\x1b[43mright_on\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mright_on\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m  10100\x1b[0m \x1b[43m        \x1b[49m\x1b[43mleft_index\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mleft_index\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m  10101\x1b[0m \x1b[43m        \x1b[49m\x1b[43mright_index\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mright_index\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m  10102\x1b[0m \x1b[43m        \x1b[49m\x1b[43msort\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43msort\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m  10103\x1b[0m \x1b[43m        \x1b[49m\x1b[43msuffixes\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43msuffixes\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m  10104\x1b[0m \x1b[43m        \x1b[49m\x1b[43mcopy\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mcopy\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m  10105\x1b[0m \x1b[43m        \x1b[49m\x1b[43mindicator\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mindicator\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m  10106\x1b[0m \x1b[43m        \x1b[49m\x1b[43mvalidate\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mvalidate\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m  10107\x1b[0m \x1b[43m    \x1b[49m\x1b[43m)\x1b[49m\n\nFile \x1b[0;32m../.venv/lib/python3.11/site-packages/pandas/core/reshape/merge.py:110\x1b[0m, in \x1b[0;36mmerge\x1b[0;34m(left, right, how, on, left_on, right_on, left_index, right_index, sort, suffixes, copy, indicator, validate)\x1b[0m\n\x1b[1;32m     93\x1b[0m \x1b[38;5;129m@Substitution\x1b[39m(\x1b[38;5;124m"\x1b[39m\x1b[38;5;130;01m\\n\x1b[39;00m\x1b[38;5;124mleft : DataFrame or named Series\x1b[39m\x1b[38;5;124m"\x1b[39m)\n\x1b[1;32m     94\x1b[0m \x1b[38;5;129m@Appender\x1b[39m(_merge_doc, indents\x1b[38;5;241m=\x1b[39m\x1b[38;5;241m0\x1b[39m)\n\x1b[1;32m     95\x1b[0m \x1b[38;5;28;01mdef\x1b[39;00m \x1b[38;5;21mmerge\x1b[39m(\n\x1b[0;32m   (...)\x1b[0m\n\x1b[1;32m    108\x1b[0m     validate: \x1b[38;5;28mstr\x1b[39m \x1b[38;5;241m|\x1b[39m \x1b[38;5;28;01mNone\x1b[39;00m \x1b[38;5;241m=\x1b[39m \x1b[38;5;28;01mNone\x1b[39;00m,\n\x1b[1;32m    109\x1b[0m ) \x1b[38;5;241m-\x1b[39m\x1b[38;5;241m>\x1b[39m DataFrame:\n\x1b[0;32m--> 110\x1b[0m     op \x1b[38;5;241m=\x1b[39m \x1b[43m_MergeOperation\x1b[49m\x1b[43m(\x1b[49m\n\x1b[1;32m    111\x1b[0m \x1b[43m        \x1b[49m\x1b[43mleft\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m    112\x1b[0m \x1b[43m        \x1b[49m\x1b[43mright\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m    113\x1b[0m \x1b[43m        \x1b[49m\x1b[43mhow\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mhow\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m    114\x1b[0m \x1b[43m        \x1b[49m\x1b[43mon\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mon\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m    115\x1b[0m \x1b[43m        \x1b[49m\x1b[43mleft_on\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mleft_on\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m    116\x1b[0m \x1b[43m        \x1b[49m\x1b[43mright_on\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mright_on\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m    117\x1b[0m \x1b[43m        \x1b[49m\x1b[43mleft_index\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mleft_index\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m    118\x1b[0m \x1b[43m        \x1b[49m\x1b[43mright_index\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mright_index\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m    119\x1b[0m \x1b[43m        \x1b[49m\x1b[43msort\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43msort\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m    120\x1b[0m \x1b[43m        \x1b[49m\x1b[43msuffixes\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43msuffixes\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m    121\x1b[0m \x1b[43m        \x1b[49m\x1b[43mindicator\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mindicator\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m    122\x1b[0m \x1b[43m        \x1b[49m\x1b[43mvalidate\x1b[49m\x1b[38;5;241;43m=\x1b[39;49m\x1b[43mvalidate\x1b[49m\x1b[43m,\x1b[49m\n\x1b[1;32m    123\x1b[0m \x1b[43m    \x1b[49m\x1b[43m)\x1b[49m\n\x1b[1;32m    124\x1b[0m     \x1b[38;5;28;01mreturn\x1b[39;00m op\x1b[38;5;241m.\x1b[39mget_result(copy\x1b[38;5;241m=\x1b[39mcopy)\n\nFile \x1b[0;32m../.venv/lib/python3.11/site-packages/pandas/core/reshape/merge.py:713\x1b[0m, in \x1b[0;36m_MergeOperation.__init__\x1b[0;34m(self, left, right, how, on, left_on, right_on, axis, left_index, right_index, sort, suffixes, indicator, validate)\x1b[0m\n\x1b[1;32m    709\x1b[0m \x1b[38;5;66;03m# If argument passed to validate,\x1b[39;00m\n\x1b[1;32m    710\x1b[0m \x1b[38;5;66;03m# check if columns specified as unique\x1b[39;00m\n\x1b[1;32m    711\x1b[0m \x1b[38;5;66;03m# are in fact unique.\x1b[39;00m\n\x1b[1;32m    712\x1b[0m \x1b[38;5;28;01mif\x1b[39;00m validate \x1b[38;5;129;01mis\x1b[39;00m \x1b[38;5;129;01mnot\x1b[39;00m \x1b[38;5;28;01mNone\x1b[39;00m:\n\x1b[0;32m--> 713\x1b[0m     \x1b[38;5;28;43mself\x1b[39;49m\x1b[38;5;241;43m.\x1b[39;49m\x1b[43m_validate\x1b[49m\x1b[43m(\x1b[49m\x1b[43mvalidate\x1b[49m\x1b[43m)\x1b[49m\n\nFile \x1b[0;32m../.venv/lib/python3.11/site-packages/pandas/core/reshape/merge.py:1510\x1b[0m, in \x1b[0;36m_MergeOperation._validate\x1b[0;34m(self, validate)\x1b[0m\n\x1b[1;32m   1508\x1b[0m \x1b[38;5;28;01mif\x1b[39;00m validate \x1b[38;5;129;01min\x1b[39;00m [\x1b[38;5;124m"\x1b[39m\x1b[38;5;124mone_to_one\x1b[39m\x1b[38;5;124m"\x1b[39m, \x1b[38;5;124m"\x1b[39m\x1b[38;5;124m1:1\x1b[39m\x1b[38;5;124m"\x1b[39m]:\n\x1b[1;32m   1509\x1b[0m     \x1b[38;5;28;01mif\x1b[39;00m \x1b[38;5;129;01mnot\x1b[39;00m left_unique \x1b[38;5;129;01mand\x1b[39;00m \x1b[38;5;129;01mnot\x1b[39;00m right_unique:\n\x1b[0;32m-> 1510\x1b[0m         \x1b[38;5;28;01mraise\x1b[39;00m MergeError(\n\x1b[1;32m   1511\x1b[0m             \x1b[38;5;124m"\x1b[39m\x1b[38;5;124mMerge keys are not unique in either left \x1b[39m\x1b[38;5;124m"\x1b[39m\n\x1b[1;32m   1512\x1b[0m             \x1b[38;5;124m"\x1b[39m\x1b[38;5;124mor right dataset; not a one-to-one merge\x1b[39m\x1b[38;5;124m"\x1b[39m\n\x1b[1;32m   1513\x1b[0m         )\n\x1b[1;32m   1514\x1b[0m     \x1b[38;5;28;01melif\x1b[39;00m \x1b[38;5;129;01mnot\x1b[39;00m left_unique:\n\x1b[1;32m   1515\x1b[0m         \x1b[38;5;28;01mraise\x1b[39;00m MergeError(\n\x1b[1;32m   1516\x1b[0m             \x1b[38;5;124m"\x1b[39m\x1b[38;5;124mMerge keys are not unique in left dataset; not a one-to-one merge\x1b[39m\x1b[38;5;124m"\x1b[39m\n\x1b[1;32m   1517\x1b[0m         )\n\n\x1b[0;31mMergeError\x1b[0m: Merge keys are not unique in either left or right dataset; not a one-to-one merge\n')>
Traceback (most recent call last):
  File "../.venv/lib/python3.11/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
         ^^^^^^^^^^^^^^^^
  File "../.venv/lib/python3.11/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "../.venv/lib/python3.11/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "../.venv/lib/python3.11/site-packages/click/decorators.py", line 33, in new_func
    return f(get_current_context(), *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "../.venv/lib/python3.11/site-packages/papermill/cli.py", line 235, in papermill
    execute_notebook(
  File "../.venv/lib/python3.11/site-packages/papermill/execute.py", line 116, in execute_notebook
    nb = papermill_engines.execute_notebook_with_engine(
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "../.venv/lib/python3.11/site-packages/papermill/engines.py", line 48, in execute_notebook_with_engine
    return self.get_engine(engine_name).execute_notebook(nb, kernel_name, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "../.venv/lib/python3.11/site-packages/papermill/engines.py", line 370, in execute_notebook
    cls.execute_managed_notebook(nb_man, kernel_name, log_output=log_output, **kwargs)
  File "../.venv/lib/python3.11/site-packages/ploomber_core/telemetry/telemetry.py", line 700, in wrapper
    result = func(*args, **kwargs)
             ^^^^^^^^^^^^^^^^^^^^^
  File "../.venv/lib/python3.11/site-packages/ploomber_engine/engine.py", line 53, in execute_managed_notebook
    return PapermillPloomberNotebookClient(nb_man, **final_kwargs).execute()
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "../.venv/lib/python3.11/site-packages/papermill/clientwrap.py", line 45, in execute
    self.papermill_execute_cells()
  File "../.venv/lib/python3.11/site-packages/ploomber_engine/papermill.py", line 30, in papermill_execute_cells
    self.execute_cell(cell, index)
  File "../.venv/lib/python3.11/site-packages/jupyter_core/utils/__init__.py", line 165, in wrapped
    return loop.run_until_complete(inner)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "../.conda_env/lib/python3.11/asyncio/base_events.py", line 641, in run_until_complete
    self.run_forever()
  File "../.conda_env/lib/python3.11/asyncio/base_events.py", line 608, in run_forever
    self._run_once()
  File "../.conda_env/lib/python3.11/asyncio/base_events.py", line 1898, in _run_once
    event_list = self._selector.select(timeout)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "../.conda_env/lib/python3.11/selectors.py", line 468, in select
    fd_event_list = self._selector.poll(timeout, max_ev)
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
KeyboardInterrupt

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "../.venv/lib/python3.11/site-packages/ploomber_engine/client.py", line 227, in async_execute_cell
    await self._check_raise_for_error(cell, cell_index, exec_reply)
  File "../.venv/lib/python3.11/site-packages/nbclient/client.py", line 918, in _check_raise_for_error
    raise CellExecutionError.from_cell_and_msg(cell, exec_reply_content)
nbclient.exceptions.CellExecutionError: An error occurred while executing the following cell:
------------------
import pandas as pd

for foo in ["bar", "baz"]:
    pd.DataFrame({'foo': [1, 1]}).merge(pd.DataFrame({'foo': [1, 1]}), how="left", on="foo", validate="1:1")
------------------

----- stdout -----
> ../.venv/lib/python3.11/site-packages/pandas/core/reshape/merge.py(1510)_validate()
   1508         if validate in ["one_to_one", "1:1"]:
   1509             if not left_unique and not right_unique:
-> 1510                 raise MergeError(
   1511                     "Merge keys are not unique in either left "
   1512                     "or right dataset; not a one-to-one merge"

----- stdout -----
--KeyboardInterrupt--

KeyboardInterrupt: Interrupted by user
------------------

---------------------------------------------------------------------------
MergeError                                Traceback (most recent call last)
Cell In[2], line 4
      1 import pandas as pd
      3 for foo in ["bar", "baz"]:
----> 4     pd.DataFrame({'foo': [1, 1]}).merge(pd.DataFrame({'foo': [1, 1]}), how="left", on="foo", validate="1:1")

File ../.venv/lib/python3.11/site-packages/pandas/core/frame.py:10093, in DataFrame.merge(self, right, how, on, left_on, right_on, left_index, right_index, sort, suffixes, copy, indicator, validate)
  10074 @Substitution("")
  10075 @Appender(_merge_doc, indents=2)
  10076 def merge(
   (...)
  10089     validate: str | None = None,
  10090 ) -> DataFrame:
  10091     from pandas.core.reshape.merge import merge
> 10093     return merge(
  10094         self,
  10095         right,
  10096         how=how,
  10097         on=on,
  10098         left_on=left_on,
  10099         right_on=right_on,
  10100         left_index=left_index,
  10101         right_index=right_index,
  10102         sort=sort,
  10103         suffixes=suffixes,
  10104         copy=copy,
  10105         indicator=indicator,
  10106         validate=validate,
  10107     )

File ../.venv/lib/python3.11/site-packages/pandas/core/reshape/merge.py:110, in merge(left, right, how, on, left_on, right_on, left_index, right_index, sort, suffixes, copy, indicator, validate)
     93 @Substitution("\nleft : DataFrame or named Series")
     94 @Appender(_merge_doc, indents=0)
     95 def merge(
   (...)
    108     validate: str | None = None,
    109 ) -> DataFrame:
--> 110     op = _MergeOperation(
    111         left,
    112         right,
    113         how=how,
    114         on=on,
    115         left_on=left_on,
    116         right_on=right_on,
    117         left_index=left_index,
    118         right_index=right_index,
    119         sort=sort,
    120         suffixes=suffixes,
    121         indicator=indicator,
    122         validate=validate,
    123     )
    124     return op.get_result(copy=copy)

File ../.venv/lib/python3.11/site-packages/pandas/core/reshape/merge.py:713, in _MergeOperation.__init__(self, left, right, how, on, left_on, right_on, axis, left_index, right_index, sort, suffixes, indicator, validate)
    709 # If argument passed to validate,
    710 # check if columns specified as unique
    711 # are in fact unique.
    712 if validate is not None:
--> 713     self._validate(validate)

File ../.venv/lib/python3.11/site-packages/pandas/core/reshape/merge.py:1510, in _MergeOperation._validate(self, validate)
   1508 if validate in ["one_to_one", "1:1"]:
   1509     if not left_unique and not right_unique:
-> 1510         raise MergeError(
   1511             "Merge keys are not unique in either left "
   1512             "or right dataset; not a one-to-one merge"
   1513         )
   1514     elif not left_unique:
   1515         raise MergeError(
   1516             "Merge keys are not unique in left dataset; not a one-to-one merge"
   1517         )

MergeError: Merge keys are not unique in either left or right dataset; not a one-to-one merge

To summarize: the MergeError I'm hoping to debug has already occurred, but somehow Python is stuck elsewhere.