Strip the timestamps and function names from extcap errors before
displaying them in a dialog. This keeps us from spewing
```
Error by extcap pipe: ** (falcodump:24913) 15:08:20.263535 [falcodump
WARNING] extcap/falcodump.cpp:593 -- main(): cloudtrail plugin error:
failed to list objects: ExpiredToken: The provided token has expired.
status code: 400, request id: M2PYJOT4JGVAA6B9, host id:
+4V8Q+DGV+80Jd3fdc7tODyVdTRvepNgCD9zuvXeL7kzvp2oikaoi9CLMW+UKt/
aR1G2UXIqyQ8=
```
at the user.
Check for warning messages and set our dialog type accordingly.