fix integration test for mismatched python version

tests/integration/workflows/python_pip/test_python_pip.py

@@ -1,5 +1,6 @@
 import os
 import shutil
+import six
 import sys
 import platform
 import tempfile
@@ -137,7 +138,15 @@ def test_mismatch_runtime_python_project(self):
                 runtime=self.runtime_mismatch[self.runtime],
             )
         except WorkflowFailedError as ex:
-            self.assertIn("Binary validation failed", str(ex))
+            # handle both e.g. missing /usr/bin/python2.7 and situation where
+            # python2.7 does not have pip installed (as is the case in some
+            # Mac environments)
+            ex_s = str(ex)
+            if (
+                "Binary validation failed" not in ex_s
+                and "pip executable not found in your python environment" not in ex_s
+            ):
+                six.raise_from(AssertionError("Unexpected exception"), ex)
 
     def test_runtime_validate_python_project_fail_open_unsupported_runtime(self):
         with self.assertRaises(WorkflowFailedError):