Merge remote-tracking branch 'origin/u/dkrenn/k-regular-warning' into regular-sequences-mul

* origin/u/dkrenn/k-regular-warning: (69 commits)
  fix doctests after merge
  test RuntimeError no invertible matrix
  add comment and ref to #35748
  remove W293 blank line contains whitespace
  fix docstring (LaTeX)
  fix whitespaces
  better handling of n_max
  add another test
  add another test
  fixup n_max
  fix left/right issue when bootstraping guessing
  more consistent naming in DEBUG output
  consequently rename to linear_combination
  simplify code by removing variables
  make NoLinearCombination a RuntimeError
  remove unneeded import
  Apply suggestions from code review
  Apply suggestions from code review
  write error message
  rename, describe and test max_exponent
  ...

Author: dkrenn