Fixed #28628 --Replaced '\d' in regexes with [0-9] for more strict matching.

[JunyiJ]

In Python2 and Python3 '\d' in regular expression matches to different patterns. To avoid errors, '\d' was replaced with [0-9].

[wkschwartz]

The matching rules for \d are identical in Pythons 2 and 3. In both versions, u'\d' matches Unicode decimal characters and b'\d' matches b'[0-9]'. Unless some test started failing or you have a particular use case that's stopped working, I'm not sure this PR is necessary. Personally, I find \d more legible than [0-9].

[JunyiJ]

Based on Python3's document, what '\d' corresponding to is slightly different from Python2:

Matches any Unicode decimal digit (that is, any character in Unicode character category [Nd]). This includes [0-9], and also many other digit characters.

However, I actually kind of agree with you that '\d' seems to be more robust. But if someone intended to use only [0-9], she/he might meet problem with the current version of django.

[timgraham]

It would be good to add tests to show what benefit each change has.

[timgraham]

Junyi, do you want to move forward with this or should we close it? Absent some tests to show some benefit, I'm not sure.

[JunyiJ]

Hi, @timgraham. You can close it. Thanks!