bpo-30167: Prevent site.main() exception if PYTHONSTARTUP is set. (GH-6731) (GH-7606)

Before Python 3.6, os.path.abspath(None) used to report an AttributeError which was properly caught inside site.abs_paths, making it ignore __main__, one of sys.modules, which has __file__ and __cached__ set to None. With 3.6, os.path.abspath(None) raises TypeError instead which site.abs_path was not expecting.  This resulted in an uncaught exception if a user had PYTHONSTARTUP set and the application called site.main() which a number of third-party programs do.
(cherry picked from commit 2487f30d55)

Co-authored-by: Steve Weber <steverweber@gmail.com>

Lib/site.py

@@ -104,11 +104,11 @@ def abs_paths():
             continue   # don't mess with a PEP 302-supplied __file__
         try:
             m.__file__ = os.path.abspath(m.__file__)
-        except (AttributeError, OSError):
+        except (AttributeError, OSError, TypeError):
             pass
         try:
             m.__cached__ = os.path.abspath(m.__cached__)
-        except (AttributeError, OSError):
+        except (AttributeError, OSError, TypeError):
             pass
 
 

Misc/ACKS

@@ -1713,6 +1713,7 @@ David Watson
 Aaron Watters
 Henrik Weber
 Leon Weber
+Steve Weber
 Corran Webster
 Glyn Webster
 Phil Webster

Misc/NEWS.d/next/Library/2018-06-10-19-29-17.bpo-30167.G5EgC5.rst

@@ -0,0 +1 @@
+Prevent site.main() exception if PYTHONSTARTUP is set. Patch by Steve Weber.