dist/tools/mkconstfs: fix various flake8 issues
dist/tools/mkconstfs: fix various flake8 issues

Josar/RIOT,Josar/RIOT,kaspar030/RIOT,josephnoir/RIOT,BytesGalore/RIOT,kbumsik/RIOT,OlegHahm/RIOT,toonst/RIOT,mtausig/RIOT,avmelnikoff/RIOT,kaspar030/RIOT,OlegHahm/RIOT,yogo1212/RIOT,miri64/RIOT,neiljay/RIOT,gebart/RIOT,A-Paul/RIOT,jasonatran/RIOT,yogo1212/RIOT,smlng/RIOT,BytesGalore/RIOT,LudwigKnuepfer/RIOT,neiljay/RIOT,gebart/RIOT,kbumsik/RIOT,x3ro/RIOT,immesys/RiSyn,kaspar030/RIOT,x3ro/RIOT,kYc0o/RIOT,smlng/RIOT,cladmi/RIOT,roberthartung/RIOT,Josar/RIOT,yogo1212/RIOT,basilfx/RIOT,BytesGalore/RIOT,miri64/RIOT,OlegHahm/RIOT,lazytech-org/RIOT,avmelnikoff/RIOT,kaspar030/RIOT,mtausig/RIOT,LudwigKnuepfer/RIOT,basilfx/RIOT,OTAkeys/RIOT,biboc/RIOT,neiljay/RIOT,aeneby/RIOT,jasonatran/RIOT,ant9000/RIOT,kbumsik/RIOT,smlng/RIOT,LudwigKnuepfer/RIOT,RIOT-OS/RIOT,biboc/RIOT,toonst/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,roberthartung/RIOT,rfuentess/RIOT,toonst/RIOT,basilfx/RIOT,aeneby/RIOT,LudwigKnuepfer/RIOT,A-Paul/RIOT,gebart/RIOT,josephnoir/RIOT,cladmi/RIOT,ant9000/RIOT,LudwigOrtmann/RIOT,aeneby/RIOT,neiljay/RIOT,A-Paul/RIOT,aeneby/RIOT,BytesGalore/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,gebart/RIOT,rfuentess/RIOT,Josar/RIOT,immesys/RiSyn,josephnoir/RIOT,immesys/RiSyn,miri64/RIOT,x3ro/RIOT,avmelnikoff/RIOT,rfuentess/RIOT,LudwigKnuepfer/RIOT,josephnoir/RIOT,lazytech-org/RIOT,avmelnikoff/RIOT,kYc0o/RIOT,cladmi/RIOT,jasonatran/RIOT,yogo1212/RIOT,authmillenon/RIOT,toonst/RIOT,RIOT-OS/RIOT,ant9000/RIOT,kYc0o/RIOT,miri64/RIOT,RIOT-OS/RIOT,lazytech-org/RIOT,mtausig/RIOT,x3ro/RIOT,ant9000/RIOT,authmillenon/RIOT,OTAkeys/RIOT,kbumsik/RIOT,mtausig/RIOT,neiljay/RIOT,mtausig/RIOT,kbumsik/RIOT,biboc/RIOT,mfrey/RIOT,OlegHahm/RIOT,roberthartung/RIOT,avmelnikoff/RIOT,biboc/RIOT,cladmi/RIOT,A-Paul/RIOT,aeneby/RIOT,LudwigOrtmann/RIOT,LudwigOrtmann/RIOT,authmillenon/RIOT,toonst/RIOT,kYc0o/RIOT,rfuentess/RIOT,A-Paul/RIOT,authmillenon/RIOT,basilfx/RIOT,OlegHahm/RIOT,lazytech-org/RIOT,authmillenon/RIOT,jasonatran/RIOT,mfrey/RIOT,OTAkeys/RIOT,jasonatran/RIOT,biboc/RIOT,ant9000/RIOT,immesys/RiSyn,authmillenon/RIOT,LudwigOrtmann/RIOT,mfrey/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,Josar/RIOT,mfrey/RIOT,immesys/RiSyn,basilfx/RIOT,miri64/RIOT,lazytech-org/RIOT,josephnoir/RIOT,mfrey/RIOT,x3ro/RIOT,rfuentess/RIOT,smlng/RIOT,roberthartung/RIOT,smlng/RIOT,roberthartung/RIOT,BytesGalore/RIOT,cladmi/RIOT,kaspar030/RIOT,gebart/RIOT,LudwigOrtmann/RIOT,yogo1212/RIOT,LudwigOrtmann/RIOT,immesys/RiSyn