Hello,
when preparing 3.2.0 for debian i noticed that running setup.py clean fails with

Traceback (most recent call last):
  File "./setup.py", line 247, in <module>
    long_description=long_description,
NameError: name 'long_description' is not defined

That's because https://github.com/matplotlib/matplotlib/blob/master/setup.py#L228 is only executed when https://github.com/matplotlib/matplotlib/blob/master/setup.py#L178-L180 and so it's not available when needed at https://github.com/matplotlib/matplotlib/blob/master/setup.py#L246