- Don't use %python3_only command, but properly use alternatives.

- fix the path of non-oss licensed files to remove

- set the minimal version of python to 3.5 to match upstream
requirement

- update to version 2.6.1:
* This release fixes a packaging issue. No functional changes.
- additional changes from version 2.6.0:
* Running Pygments on Python 2.x is no longer supported.
* Added lexers:
+ Linux kernel logs (PR#1310)
+ LLVM MIR (PR#1361)
+ MiniScript (PR#1397)
+ Mosel (PR#1287, PR#1326)
+ Parsing Expression Grammar (PR#1336)
+ ReasonML (PR#1386)
+ Ride (PR#1319, PR#1321)
+ Sieve (PR#1257)
+ USD (PR#1290)
+ WebIDL (PR#1309)
* Updated lexers:
+ Apache2 (PR#1378)
+ Chapel (PR#1357)
+ CSound (PR#1383)
+ D (PR#1375, PR#1362)
+ Idris (PR#1360)
+ Perl6/Raku lexer (PR#1344)
+ Python3 (PR#1382, PR#1385)