Remove python2 code

[sunwire]

Because we only support python 3, checks for Python 2 are no longer necessary.

[iredmail]

Thanks for the contribution.
Could you please fix the pep8 style issue according to GitHub Action result? Just add one more empty line. :)
https://github.com/webpy/webpy/pull/664/checks?check_run_id=910430744

[cclauss]

You can automate this process with https://github.com/asottile/pyupgrade

[iredmail]

You can automate this process with https://github.com/asottile/pyupgrade

@cclauss Thanks for sharing, i tried pyupgrade and it fixes many code style issue for my personal project. :)

[cclauss]

./web/http.py:27:1: E302 expected 2 blank lines, found 1
def prefixurl(base=""):
^
1     E302 expected 2 blank lines, found 1

[sunwire]

1     E302 expected 2 blank lines, found 1

The second commit fix it a6f563d
https://github.com/sunwire/webpy/blob/master/web/http.py#L27
I don't know why the check on github fails. Maybe because there are two commits not one.
flake8 running locally returns no errors.

[iredmail]

Merged and passed all checks. Thanks for your contribution @sunwire