Bug 1585672 - [mach] Skip modules whose __file__ attribute is None in…

… the global ImportHook r=ahal

This also gets around a flake8 lint exception.

Differential Revision: https://phabricator.services.mozilla.com/D47946

build/mach_bootstrap.py

@@ -440,7 +440,7 @@ def __call__(self, name, globals=None, locals=None, fromlist=None,
         self._modules.add(resolved_name)
 
         # Builtin modules don't have a __file__ attribute.
-        if not hasattr(module, '__file__'):
+        if not getattr(module, '__file__', None):
             return module
 
         # Note: module.__file__ is not always absolute.