don't allow crs in the code

triggered by this slipping into quantum, now that we have more windows
developers we should ensure that \r\n doesn't land in the code as
a line ending. This check prevents it.

Change-Id: I0a82be0e74915d3c3c25203db110d279580c148b

HACKING.rst

@@ -9,6 +9,7 @@ Nova Style Commandments
 General
 -------
 - Put two newlines between top-level code (funcs, classes, etc)
+- Use only UNIX style newlines ("\n"), not Windows style ("\r\n")
 - Put one newline between methods in classes and anywhere else
 - Long lines should be wrapped in parentheses
   in preference to using a backslash for line continuation.