Fix OpenSSL issue

[ryanwilsonperkin]

Fixes #446

Using twine to push a package to a repository over HTTPS recently began resulting in the following stack trace:

Traceback (most recent call last):
  File "/usr/local/bin/twine", line 6, in <module>
    from twine.__main__ import main
  File "/usr/local/lib/python3.6/site-packages/twine/__main__.py", line 23, in <module>
    from twine.cli import dispatch
  File "/usr/local/lib/python3.6/site-packages/twine/cli.py", line 23, in <module>
    import requests_toolbelt
  File "/usr/local/lib/python3.6/site-packages/requests_toolbelt/__init__.py", line 12, in <module>
    from .adapters import SSLAdapter, SourceAddressAdapter
  File "/usr/local/lib/python3.6/site-packages/requests_toolbelt/adapters/__init__.py", line 12, in <module>
    from .ssl import SSLAdapter
  File "/usr/local/lib/python3.6/site-packages/requests_toolbelt/adapters/ssl.py", line 16, in <module>
    from .._compat import poolmanager
  File "/usr/local/lib/python3.6/site-packages/requests_toolbelt/_compat.py", line 59, in <module>
    from urllib3.contrib.pyopenssl import PyOpenSSLContext
  File "/usr/local/lib/python3.6/site-packages/urllib3/contrib/pyopenssl.py", line 46, in <module>
    import OpenSSL.SSL
ModuleNotFoundError: No module named 'OpenSSL'

A recent change to requests-toolbelt results in twine attempting to reference the pyopenssl library when it is not a requirement.

While this is being addressed (requests/toolbelt#241) in requests-toolbelt, we should pin twine to the last working version.

[codecov]

Codecov Report

Merging #447 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #447   +/-   ##
=======================================
  Coverage   79.94%   79.94%           
=======================================
  Files          14       14           
  Lines         748      748           
  Branches      108      108           
=======================================
  Hits          598      598           
  Misses        113      113           
  Partials       37       37

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[ryanwilsonperkin]

After some discussion in requests/toolbelt#241 and requests/toolbelt#242 now attempting a fix in requests-toolbelt in a new PR: requests/toolbelt#243

[sigmavirus24]

0.9.1 was released which should fix this. We'd need to cut a new release to fix the version constraints. If you accept the suggestion in-line then we can cut a release that just blacklists 0.9.0 and ensures no one accidentally gets that version

[ryanwilsonperkin]

Thanks for the suggestion @sigmavirus24, applied your fix