[LGTM] C/C++ extraction always uses Python 2

[QuLogic]

When performing C/C++ extraction, LGTM tries a bunch of things, and apparently does python setup.py build. This is broken on packages that do not support Python 2, e.g., https://lgtm.com/projects/g/matplotlib/matplotlib/logs/languages/lang:cpp

I tried explicitly setting Python 3, but this apparently did not affect the C/C++ side.

PS, why is it so hard to figure out where to report issues with LGTM? I'm not even sure if this is the right place.

[tausbn]

For this particular case, you could try one of two things

1. Invoking python3 setup.py build directly by setting the configure step for cpp
2. Explicitly modifying the PATH variable to put the Python 3 interpreter first. For this, something like putting

cp `which python3` $LGTM_WORKSPACE/python
PATH=$LGTM_WORKSPACE:$PATH

in the before_index step might work.

(Note: I have not tested the two approaches above. If they don't work, do let us know.)

[QuLogic]

I tried a test build with the first option, which seems to work. Now I need to figure out how to get the download part working.