Unable to parse stub platform conditionals

[tharvik]

In PEP 484, there is a section on conditional stubs.

For example, the next code is a valid stub code

import sys

if sys.platform == 'win32':
    def windows_def_only() -> None: ...

But currently, running pytd on it will fail with

Error while parsing pyi:
  File "/tmp/asd.pyi", line 3
    if sys.platform == 'win32':
                        ^
SyntaxError: Unexpected 'NAME'

[matthiaskramm]

Fixed in our local version. We're exporting the fix now.

[matthiaskramm]

Fix pushed.