Sanitize message causes exception when trying to parse errors.

[jordwalke]

Here's the error that the build system output. Better errors tries to parse this and fails.

SANITIZE: a total of 2 files that should probably not be in your source tree
  has been found. A script shell file
  "/Users/me/githubReasonMl/ExampleProject/_build/sanitize.sh" is being
  created. Check this script and run it to remove unwanted files or use other
  options (such as defining hygiene exceptions or using the -no-hygiene
  option).
IMPORTANT: I cannot work with leftover compiled files.
ERROR: Leftover OCaml compilation files:
  File Test.cmo in src has suffix .cmo
  File Test.cmi in src has suffix .cmi
Exiting due to hygiene violations.
Compilation unsuccessful after building 0 targets (0 cached) in 00:00:00.

Here's the stack trace that is thrown:

Fatal error: exception Failure("hd")
Raised at file "pervasives.ml", line 30, characters 22-33
Called from file "list.ml", line 23, characters 10-23
Called from file "src/reason_error_reporter.ml", line 30, characters 2-91