LGTM.com - false positive (Python regex in verbose mode)

**Description of the false positive**

In verbose regular expressions, spaces are ignored and comments are allowed. The py/regex/unmatchable-dollar and py/regex/unmatchable-caret tests give false positive.

**URL to the alert on the project page on LGTM.com**

https://lgtm.com/projects/g/2ndquadrant-it/barman/snapshot/958a76c31198ee1879d2f89ef418979c034824c7/files/barman/copy_controller.py?sort=name&dir=ASC&mode=heatmap#xfa2c7f56a58e38c9:1