Comment (by Steven R. Brandt):

It seems that the ini file reader is the thing complaining. The strings still are regular expressions, but if a regular expression is in a quoted string it should be understood with quoted string escape rules. If you prefer, we could remove the quote marks and convert \\d to \d.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2760/syntaxwarnings-raised-during-build-process