network tests are not skipped when running tests.py with --no-network

[rathann]

To help us understand and resolve your issue please check that you have provided
the information below.

• Matplotlib version, Python version and Platform (Windows, OSX, Linux ...)

1.5.2rc2, 2.7.11/3.5.1, Fedora rawhide

• How did you install Matplotlib and Python (pip, anaconda, from source ...)

From source.

• If possible please supply a Short, Self Contained, Correct, Example
  that demonstrates the issue i.e a small piece of code which reproduces the issue
  and can be run with out any other (or as few as possible) external dependencies.

python2 tests.py --no-network

or

python3 tests.py --no-network

The following tests are failing:

• lib/matplotlib/tests/test_image.py:549 test_load_from_url()
• lib/matplotlib/tests/test_style.py:60 test_use_url()

[tacaswell]

attn @mdboom

I took a pass at this and lost to nose.

[tacaswell]

ok, took a second pass and won (not sure why but eh).