InvalidRequirement - possible requirement parsing regression in 8.1.2

• Pip version: 8.1.2
• Python version: 2.7.11
• Operating System: Debian Jesse (official python:2.7 Docker image)

Description:

When trying to install the requirement appdynamics I get the error below. This package has a requirements.txt format which I have never seen before: https://pypi.python.org/pypi/appdynamics/4.1.4.0

appdynamics-bindeps-linux-x86 (==4.1.4.0); 'linux' in sys_platform and platform_machine=='i386'
appdynamics-bindeps-linux-x64 (==4.1.4.0); 'linux' in sys_platform and (platform_machine=='x86_64' or platform_machine=='AMD64')
appdynamics-bindeps-osx-x86 (==4.1.4.0); sys_platform=='darwin' and platform_machine=='i386'
appdynamics-bindeps-osx-x64 (==4.1.4.0); sys_platform=='darwin' and (platform_machine=='x86_64' or platform_machine=='AMD64')

What I’ve run:

Error

docker run --rm -it python:2.7 bash
pip install appdynamics

Traceback

Invalid requirement: 'appdynamics-proxysupport-linux-x64==1.8.0.51; linux in "sys_platform" and (platform_machine == "x86_64" or platform_machine == "AMD64")'
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/pip/req/req_install.py", line 78, in __init__
    req = Requirement(req)
  File "/usr/local/lib/python2.7/site-packages/pip/_vendor/packaging/requirements.py", line 96, in __init__
    requirement_string[e.loc:e.loc + 8]))
InvalidRequirement: Invalid requirement, parse error at "'; linux '"

No Error

docker run --rm -it python:2.7 bash
pip install --upgrade pip==8.1.1
pip install appdynamics  # works

[gsnedders]

I guess we need to add support to packaging for this quirk, if packages are relying on it. Yay. :\ (Though trust anything @dstufft says over me.)

[KoviRobi]

For Plover at least, the ‘in’ syntax is what is broken, so using "win" == sys_platform instead of "win" in sys_platform works.