I got just the thing for you:

https://gist.github.com/hraban/10c7f72ba6ec55247f2d

Every time you write some code you need to remember removing before commit, surround it with a comment containing "NOCOMMIT". With this script as a pre-commit hook, git will echo an error message and fail.

E.g.:

  print("debug: ", myval)

becomes:

  print("debug: ", myval) # NOCOMMIT

I end up relying on this every day I program. Can't go back.