Improve error message for strings with conflicting prefixes

[sobolevn]

Feature or enhancement

Right now it is:

>>> ft'a'
  File "<python-input-3>", line 1
    ft'a'
      ^^^
SyntaxError: invalid syntax

I propose:

>>> ft'a'
  File "<python-input-3>", line 1
    ft'a'
      ^^^
SyntaxError: can't use both "f" and "t" prefixes for strings at the same time

cc @lysnikolaou

I am working on the issue :)

Linked PRs

• gh-133197: Improve error message for ft"" and bt"" cases #133202
• gh-133197: Improve error message for incompatible string / bytes prefixes #133242

[terryjreedy]

More tersely, "f" and "t" prefixes are incompatible.

[sobolevn]

I can change the one I commited when working on new ones. I like your suggestion! Thanks!