We observed lines in our logs where the timestamp field was still
respecting the timestamp regexp, so the line was not reported as
invalid, but parsing such timestamp caused a ValueError in
_matchToDateTime

The beginning of line was:
127.0.0.1 - - [14/Jul/2017:127.0.0.1 - - [14/Jul/2017:09:41:41 +0200]

Which uses `[14/Jul/2017:127.0.0.1 - - [14/Jul/2017:09:41:41 +0200]` as
timestamp, so this fail the simple .split() used to separate timestamp
and timezone.

Added a minimal test case to reproduce this specific problem.