Allow the 'clean' command to run

[benjaoming]

Summary

Getting rid of this error more permanently (although also disabled the clean command in debian/rules)

make[1]: Entering directory '/ka-lite-installers/debian/build/ka-lite-source-0.17.4'
rm -rf ka_lite_static.egg-info
python setup.py clean -a
Already blocking...
Already blocking...
Traceback (most recent call last):
  File "setup.py", line 289, in <module>
    "Already installed ka-lite so cannot install ka-lite-static. "
RuntimeError: Already installed ka-lite so cannot install ka-lite-static. Remove existing ka-lite-static packages, for instance using 

    pip uninstall ka-lite-static  # Standard
    sudo apt-get remove ka-lite  # Ubuntu/Debian

...or other possible installation mechanisms you may have been using.
debian/rules:8: recipe for target 'override_dh_auto_clean' failed

TODO

If not all TODOs are marked, this PR is considered WIP (work in progress)

• [x] Has documentation been written/updated?
• [x] Have you written release notes for the upcoming release?

Reviewer guidance

Non really, 0.17.4 is out, so this is for the next, and not really important

Issues addressed

n/a

[codecov[bot]]

Codecov Report

Merging #5560 into 0.17.x will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           0.17.x    #5560   +/-   ##
=======================================
  Coverage   66.13%   66.13%           
=======================================
  Files         113      113           
  Lines        6506     6506           
=======================================
  Hits         4303     4303           
  Misses       2203     2203

---

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[benjaoming]

Turns out I had added a development version of KA Lite in /usr/local/lib/python2.7/dist-packages/easy-install.pth