python 3.6 f-string prefix not recognized

Issue #1452 new
Tyler Makaro
created an issue

'u','b','r','rb','br' (and their capitalized variants) are parsed by the Python 3 lexer as Token.Literal.String.Affix.

'f','rf','fr' (and their capitalized variants) are parsed as Token.Name.

To reproduce:

from pygments.lexer.python import Python3Lexer
lexer = Python3Lexer()

code1 = 'f"str"'
code2 = 'r"str"'
print(list(lexer.get_tokens(code1)))
print(list(lexer.get_tokens(code2)))

code2 tokenizes fine, but code 1 tokenizes wrongly.