Simplify regexes

[kinow]

When using [...] in regexes, I believe we do not need to escape ., :, ), <, >, etc. As far as I know, we need to escape only the closing ], and the normal sequences like \n, \r, \t.

Python regex engine does the job of escaping these character anyway, but being regexes not always the fastest option, perhaps removing unnecessary escapes is a good idea?

Also included one more change (second commit) to use ([`\]) instead of (`|\). For two characters it makes no difference performance-wise. With more characters [`\] would probably be faster. But it's still easier to read I think?

Low priority, for Cylc 8 or later, without backport to Cylc 7 (I do not think it's necessary for the 7.8.x release series).

Cheers
Bruno

[kinow]

Waited for Travis-CI to build the branch in my repository. If it fails here, it's one of those flaky tests, and Travis will need a kick.

[matthewrmshin]

Yes. For completeness, the only other character that needs escaping in [...] is the hyphen/minus sign -, which is used in syntax like [a-z].

The only other thing we can do is to improve performance of regular expression logic is to pre-compile them where possible. (Not sure if this is still true or not.)

This change looks like good to go.

[hjoliver]

Two approvals (and @oliver-sanders seems to agree!)