When cleaning up comments from lines of the form:
foo bar # this is a comment
You want to remove remove everything after the first comment character
not after the last comment character. This is because:
foo bar # this is # a comment
Should get everything after bar removed not everything after is.
Unfortunately when you use str.rfind() you remove everything after is
not everything after bar. Switch to regular trusty find to fix this.
Change-Id: I78aa6b51b5be03bd3b8ce7885415442171218977
7f35178617