concurrent schema test writes can break

[drewbanin]

ompiled 2 models, 2 tests, 0 archives, 0 analyses, 12 macros
Concurrency: 2 threads (target='dev')

09:14:25 | Running 2 tests
09:14:25 |
09:14:25 | 1 of 2 START test not_null_integers_i................................ [RUN]
09:14:25 | 2 of 2 START test unique_integers_i.................................. [RUN]
09:14:26 | 2 of 2 PASS unique_integers_i........................................ [PASS in 0.01s]
Traceback (most recent call last):
  File "/usr/local/bin/dbt", line 11, in <module>
    load_entry_point('dbt==0.8.0', 'console_scripts', 'dbt')()
  File "/usr/local/Cellar/dbt/0.8.0/libexec/lib/python3.6/site-packages/dbt/main.py", line 28, in main
    handle(args)
  File "/usr/local/Cellar/dbt/0.8.0/libexec/lib/python3.6/site-packages/dbt/main.py", line 46, in handle
    res = run_from_args(parsed)
  File "/usr/local/Cellar/dbt/0.8.0/libexec/lib/python3.6/site-packages/dbt/main.py", line 100, in run_from_args
    result = task.run()
  File "/usr/local/Cellar/dbt/0.8.0/libexec/lib/python3.6/site-packages/dbt/task/test.py", line 31, in run
    results = runner.run_tests(include, exclude, set())
  File "/usr/local/Cellar/dbt/0.8.0/libexec/lib/python3.6/site-packages/dbt/runner.py", line 852, in run_tests
    flatten_graph=True)
  File "/usr/local/Cellar/dbt/0.8.0/libexec/lib/python3.6/site-packages/dbt/runner.py", line 831, in run_types_from_graph
    on_failure, should_run_hooks)
  File "/usr/local/Cellar/dbt/0.8.0/libexec/lib/python3.6/site-packages/dbt/runner.py", line 696, in execute_nodes
    for node in nodes_to_execute]):
  File "/usr/local/opt/python3/Frameworks/Python.framework/Versions/3.6/lib/python3.6/multiprocessing/pool.py", line 699, in next
    raise value
  File "/usr/local/opt/python3/Frameworks/Python.framework/Versions/3.6/lib/python3.6/multiprocessing/pool.py", line 119, in worker
    result = (True, func(*args, **kwds))
  File "/usr/local/Cellar/dbt/0.8.0/libexec/lib/python3.6/site-packages/dbt/runner.py", line 577, in safe_execute_node
    raise e
  File "/usr/local/Cellar/dbt/0.8.0/libexec/lib/python3.6/site-packages/dbt/runner.py", line 535, in safe_execute_node
    node = compiler.compile_node(node, flat_graph)
  File "/usr/local/Cellar/dbt/0.8.0/libexec/lib/python3.6/site-packages/dbt/compilation.py", line 323, in compile_node
    injected_node['wrapped_sql'])
  File "/usr/local/Cellar/dbt/0.8.0/libexec/lib/python3.6/site-packages/dbt/compilation.py", line 166, in __write
    os.makedirs(os.path.dirname(target_path))
  File "/usr/local/Cellar/dbt/0.8.0/libexec/bin/../lib/python3.6/os.py", line 220, in makedirs
    mkdir(name, mode)
FileExistsError: [Errno 17] File exists: 'target/build/test_project/schema_test'

Because of this code:

        if not os.path.exists(os.path.dirname(target_path)):
            os.makedirs(os.path.dirname(target_path))

We can just catch the FileExistsError. Does anything like this happen elsewhere?

[drewbanin]

fixed: #398