Python 3.5 is bitrotten

[nottombrown]

See this failure in CI

Traceback:
../../../miniconda/envs/test-environment/lib/python3.5/site-packages/skimage/__init__.py:121: in <module>
    from ._shared import geometry
E   ImportError: dlopen: cannot load any more object with static TLS
During handling of the above exception, another exception occurred:
unrestricted-advex/unrestricted_advex/tests/test_two_class_mnist.py:3: in <module>
    from unrestricted_advex import eval_kit, attacks
unrestricted-advex/unrestricted_advex/eval_kit.py:13: in <module>
    from unrestricted_advex import attacks, plotting
unrestricted-advex/unrestricted_advex/attacks.py:18: in <module>
    from imagenet_c import corrupt
../../../miniconda/envs/test-environment/lib/python3.5/site-packages/imagenet_c/__init__.py:3: in <module>
    from .corruptions import *
../../../miniconda/envs/test-environment/lib/python3.5/site-packages/imagenet_c/corruptions.py:8: in <module>
    import skimage as sk
../../../miniconda/envs/test-environment/lib/python3.5/site-packages/skimage/__init__.py:124: in <module>
    _raise_build_error(e)
../../../miniconda/envs/test-environment/lib/python3.5/site-packages/skimage/__init__.py:104: in _raise_build_error
    %s""" % (e, msg))
E   ImportError: dlopen: cannot load any more object with static TLS
E   It seems that scikit-image has not been built correctly.
E   
E   Your install of scikit-image appears to be broken.
E   Try re-installing the package following the instructions at:
E   https://scikit-image.org/docs/stable/install.html

https://travis-ci.org/google/unrestricted-adversarial-examples/builds/625054022?utm_source=github_status&utm_medium=notification

I suspect that this error comes from a bad version of tensorflow / scikit image, or from an improper import order. Would welcome contributions fixing CI!