Re-enable TestProxies tests

What is the expected behavior?

Related to Qiskit/qiskit-ibm-provider#304 Currently, test.ibmq.test_proxies.TestProxies tests are skipped using @skipIf decorator

@skipIf(sys.version_info >= (3, 7), 'pproxy version not supported in 3.7')

The tests can be re-enabled if we update pproxy package from version 1.2.2 to 2.1.8 in requirements-dev.txt file. Then, test.ibmq.test_proxies.TestProxies can be run under >= 3.7 python versions.

[diego-plan9]

Yes, using pip conditionals was the exploration I hinted at by the “play a bit with pip and make it install versions intelligently” !

We are already checking for python version in the test itself and it would be pretty isolated, so there is no worry adding the additional checking and fine-tuning of that parameter - as a matter of fact, some tweaking of the skipping will also be needed to account for invalid combinations of python version + pproxy version (mostly for keeping the test suite runnable even under unusual circumstances).

[yeralin]

There is another solution I thought of @diego-plan9

pproxy==1.2.2; python_version <= '3.5'
pproxy==2.1.8; python_version > '3.5'

How does this look to you?

UPD: The only complication with this approach is that pproxy==1.2.2 uses -i flag for passing an address, and pproxy==2.1.8 uses -l flag 😞

That would require some checking of python version at runtime:

from sys import version_info as vi

if (vi[0], vi[1]) <= (3,5):
    listening_flag = '-i'
else:
    listening_flag = '-l'