Warnings with simplified character classes have extra backslash

[jaingaurav]

The following expression uses \w but the warning displays it as \\w

W122:VhdlLexer:root:pat#7: Overlap due to case insensitive mode
  "'[a-zA-Z_]\\w*"

[thatch]

Root cause is that we don't know the line of source (probably because it was an expression, not a literal... the indicator module only does literals right now). See regexlint/cmdline.py around line 168, there's a repr and we could use something like a raw_repr (yet to be written) here. (Actually, looking closely we should probably not shorten repr, but shorten, then repr, then deal with ellipsis.

I'd welcome a patch here, plus a trivial test.

[thatch]

Part of the work is done after rewriting consistent_repr. Basically all the cases that would output an escaped thing should raise an exception NotRepresentableAsRawstring, except Unicode could be actual characters I guess. And backslash doesn't get escaped.

Gaurav, interested in tackling or should I?