Use shell to pip to extract hashes

[peterbe]

We currently rely on _hash_of_file to extract the checksum of a package using pip. Yuck! We should use a shell and call like this:

subprocess.call(['python', '-m', 'pip', 'hash', ...])

Thanks @di for the tip!

[di]

I actually have something even better in the works, hang tight...

[di]

Hmm, seems like this won't fly with 2.6 for some reason:

$ python2.6 -m pip
/Users/di/.pyenv/versions/2.6.9/bin/python2.6: pip is a package and cannot be directly executed

works fine for other things though:

$ python2.6 -m unittest

----------------------------------------------------------------------
Ran 0 tests in 0.000s

OK

@peterbe How do you feel about officially dropping Python 2.6 support? It's nearly 5 years past end-of-life at this point. Pip itself will be dropping support for Python 2.6 with the 10.0 release as well...

[di]

Heh, looks like you already did: e655e64

[peterbe]

Thing is, about e655e64, is that it only dropped 2.6 in terms of testing in Travis. The reason was that 2.6 couldn't be installed. Neither could 3.3.

I did rearrange things in the travis and tox file. Perhaps I rushed it. So I'll try again Seems that you can get 2.6 on Travis but now it's failing on something else related to setuptools and I just don't know if I care.

@di your python2.6 -m unittest ran 0 tests :)

Would it work with your 2.6 if it has pip installed separately? I.e. download pip; cd downloaded-pip; /Users/di/.pyenv/versions/2.6.9/bin/python2.6 setup.py install
Does python2.6 -m pip work then?

[peterbe]

@di see my latest comment on #60 (comment)
Perhaps I'm just being lazy but I'm happy to just ignore 2.6 and 3.3 going forward in life.

[di]

@peterbe I think that's totally reasonable!