Colorized error messages result in hard-to-read .dump-* files

To see this, compile this file:

module Main where

x :: String -> String
x s = print (reverse s + 1)

with ghc-stage2 -ddump-tc-trace -ddump-to-file. If you look at the resulting .dump-tc-trace file with a text editor like vim, you'll see at the bottom:

...
Tc7a
checkMain fail Main main
Adding error:
  ^[[;1mBug.hs:1:1: ^[[;1m^[[31merror:^[[;1m
      The IO action ‘main’ is not defined in module ‘Main’^[[0m

The error message is now much harder to discern that before the introduction of colorized error messages.

Trac metadata

Trac field	Value
Version	8.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	Rufflewind
Operating system
Architecture