seaborn 0.4.0 doesn't install into a clean virtual environment

[dmaze]

Run:

virtualenv seaborn
. seaborn/bin/activate
pip install 'seaborn==0.4.0'

pip will download the seaborn source package and try to run its setup.py file, but in version 0.4.0 that calls check_dependencies() and raises an ImportError before pip can identify, download, and install the dependencies.

  Running setup.py (path:/ebs/home/dmaze/sea/build/seaborn/setup.py) egg_info for package seaborn

Installing collected packages: seaborn
  Running setup.py install for seaborn
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/ebs/home/dmaze/sea/build/seaborn/setup.py", line 65, in <module>
        check_dependencies()
      File "/ebs/home/dmaze/sea/build/seaborn/setup.py", line 42, in check_dependencies
        raise ImportError("seaborn requires numpy")
    ImportError: seaborn requires numpy

[mwaskom]

This is on purpose. The main dependences (numpy, scipy, and matplotlib), are all difficult to install via pip, and pip's default install_requires behavior is often poorly behaved. See #169 for the reasoning behind this approach.