Travis setup improvements

[scop]

No description provided.

[codecov]

Codecov Report

Merging #511 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #511   +/-   ##
=======================================
  Coverage   95.23%   95.23%           
=======================================
  Files         302      302           
  Lines        2558     2558           
=======================================
  Hits         2436     2436           
  Misses        122      122           

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[Gallaecio]

Looking at the conflicts, it looks like this should be simplified now to just adding 3.8 tests.

[noviluni]

Hi @scop, thank you for adding this PR! We added support for Python 3.8 and this generated conflicts, but your changes related to pip look good.

Could you solve the conflicts again? I will merge this PR just after you do it 🙌

Thanks in advance 🙂