Merge pull request #9779 from pfmoore/workaround_9540

Make pip work with warnings converted to errors

news/9779.bugfix.rst

@@ -0,0 +1 @@
+Fix pip to work with warnings converted to errors.

src/pip/__main__.py

@@ -1,5 +1,6 @@
 import os
 import sys
+import warnings
 
 # Remove '' and current working directory from the first entry
 # of sys.path, if present to avoid using current directory
@@ -18,7 +19,13 @@
     path = os.path.dirname(os.path.dirname(__file__))
     sys.path.insert(0, path)
 
-from pip._internal.cli.main import main as _main
-
 if __name__ == "__main__":
+    # Work around the error reported in #9540, pending a proper fix.
+    # Note: It is essential the warning filter is set *before* importing
+    #       pip, as the deprecation happens at import time, not runtime.
+    warnings.filterwarnings(
+        "ignore", category=DeprecationWarning, module=".*packaging\\.version"
+    )
+    from pip._internal.cli.main import main as _main
+
     sys.exit(_main())

tests/functional/test_warning.py

@@ -42,3 +42,8 @@ def test_version_warning_is_not_shown_if_python_version_is_not_2(script):
 
 def test_flag_does_nothing_if_python_version_is_not_2(script):
     script.pip("list", "--no-python-version-warning")
+
+
+def test_pip_works_with_warnings_as_errors(script):
+    script.environ['PYTHONWARNINGS'] = 'error'
+    script.pip("--version")