Fix evaluation of reciprocal trigonometric functions in even quadrants

fixes #8421
Merge pull request #8422 from skirpichev/8421-fix

Fix evaluation of reciprocal trigonometric functions in even quadrants
Add code quality test for self assignments (fixes #8362)
Code quality: don't assign to self (issue #8362)
Fix remaining self assignments
Fix py3-incompatible code
py3 fix for mailmap_update.py
Code quality: don't assign to cls (classmethod's)