* Add parts of third_party/ to pytype_test.
Pytype uses six and mypy_extensions, so these pyi files should be
tested with pytype.
* Remove newly loadable pyi files from pytype_blacklist.
All of these files can not be used with pytype at HEAD. They fail during import with various error messages. Make the test script actually load the files and all dependencies of it, instead of just verifying that it can be parsed.
This list was generated by running pytype with more options.
1: typeshed-location was pointed to the current typeshed instead of the one shipped with pytype.
2: --module-name=<foo> was provided as a parameter. Without this parameter wildcard imports "from _ast import *" misbehave.
Files with a "# parse only" comment will only be parsed and not loaded.
Rebecca Chen