pylint.sh: Ignore pylint 1.x errors regardless of the punctuation

Commit eb78c30 modified extra/pylint.sh to hide the following
messages (among others):
```
  assertion 'G_TYPE_IS_BOXED (boxed_type)' failed
  assertion 'G_IS_PARAM_SPEC (pspec)' failed
```
however on my system (Fedora 19) they appear like
```
  assertion `G_TYPE_IS_BOXED (boxed_type)' failed
  assertion `G_IS_PARAM_SPEC (pspec)' failed
```
Note the difference in punctuation: backticks instead of apostrophes.
This might be a Linux vs. BSD issue.

This commit modifies the expression to match any character instead of
apostrophes.