The re module specially handles Unicode escapes (\uXXXX and \UXXXXXXXX) so that even raw strings (r'...') have symbolic Unicode characters. But it has not supported named Unicode escapes such as r'\N{EM DASH}', making the escapes for string literals and the escapes for regular expressions asymmetric

New changeset a445feb72902e4a3c5ae712f0c289309e1580d52 by Serhiy Storchaka in branch 'master':
bpo-30688: Support \N{name} escapes in re patterns. (GH-5588)
https://github.com/python/cpython/commit/a445feb72902e4a3c5ae712f0c289309e1580d52

Thank you for your contribution Jonathan!

Hello

This leads to build failures due to circular dependency

At generate-posix-vars stage, unicodedata is imported (due to import pprint)but it has not been built due to it being a C module. However, building C modules happen after generate-posix-vars.

See full message below.

./python.exe -E -S -m sysconfig --generate-posix-vars ;\
	if test $? -ne 0 ; then \
		echo "generate-posix-vars failed" ; \
		rm -f ./pybuilddir.txt ; \
		exit 1 ; \
	fi
Traceback (most recent call last):
  File "/Users/fangyi/cpython/Lib/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/Users/fangyi/cpython/Lib/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/Users/fangyi/cpython/Lib/sysconfig.py", line 700, in <module>
    _main()
  File "/Users/fangyi/cpython/Lib/sysconfig.py", line 688, in _main
    _generate_posix_vars()
  File "/Users/fangyi/cpython/Lib/sysconfig.py", line 350, in _generate_posix_vars
    import pprint
  File "/Users/fangyi/cpython/Lib/pprint.py", line 38, in <module>
    import re
  File "/Users/fangyi/cpython/Lib/re.py", line 123, in <module>
    import sre_compile
  File "/Users/fangyi/cpython/Lib/sre_compile.py", line 14, in <module>
    import sre_parse
  File "/Users/fangyi/cpython/Lib/sre_parse.py", line 16, in <module>
    import unicodedata
ModuleNotFoundError: No module named 'unicodedata'
generate-posix-vars failed

The buidbots are broken by this.  Please fix or revert.

New changeset 5df5286abda57a0b3865d4fc3e25aaf1a820ef49 by Serhiy Storchaka (Zhou Fangyi) in branch 'master':
bpo-30688: Import unicodedata only when needed. (GH-5606)
https://github.com/python/cpython/commit/5df5286abda57a0b3865d4fc3e25aaf1a820ef49

Thank you Fangyi Zhou for your report and fix. Changes are trivial and didn't require to sign CLA.