Problems running "collectstatic" on Mac OS

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I'm using a Mac OS(El Capitan), Python 2.7 and AskBot source code from the master branch (last commit was this)!

I run into the following problem when executing python manage.py collectstatic for the first time after setting the system up as described HERE.

Traceback (most recent call last):
File "manage.py", line 10, in <module>
(...)
ImportError: dlopen([MY_PATH]/python2.7/site-packages/PIL/_imaging.so, 2): Symbol not found: _clock_gettime
Referenced from: [MY_PATH]/python2.7/site-packages/PIL/.dylibs/liblzma.5.dylib (which was built for Mac OS X 10.12)

After going crazy about it, I found HERE that there is a problem with the Pillow 5.1.0 version that is installed by default (it is not specified in the current requirements file). I'll post the solution in an answer just to make it easier for people to propose other solutions in the future.