Skip parser logic and test requiring ast.unparse in 3.8.

pytype/pyi/definitions.py

@@ -173,7 +173,9 @@ def _convert_annotated(x):
   """Convert everything to a string to store it in pytd.Annotated."""
   if isinstance(x, types.Pyval):
     return x.repr_str()
-  elif isinstance(x, astlib.AST):
+  # TODO(rechen): ast.unparse is new in Python 3.9, so we can drop the hasattr
+  # check once pytype stops supporting 3.8.
+  elif isinstance(x, astlib.AST) and hasattr(astlib, "unparse"):
     return astlib.unparse(x)
   elif isinstance(x, dict):
     return metadata.to_string(x)

pytype/pyi/parser_test.py

@@ -6,6 +6,7 @@
 from pytype.pyi import parser_test_base
 from pytype.pytd import pytd
 from pytype.tests import test_base
+from pytype.tests import test_utils
 
 import unittest
 
@@ -2846,6 +2847,7 @@ class Foo:
           y: Annotated[int, {'tag': 'call', 'fn': 'unit', 'posargs': ('s',), 'kwargs': {'exp': 9}}]
     """)
 
+  @test_utils.skipBeforePy((3, 9), "requires ast.unparse, new in 3.9")
   def test_name(self):
     self.check("""
       from typing_extensions import Annotated