[Bug 1872209] [NEW] syntax error message in f-string doesn't report line number

[Simon Lambourn]

Public bug reported:

I accidentally came across this annoying 'feature' or more likely, bug.

The following code 
   f"...foo ... {**kwargs} ..."
produces a very basic syntax error message with no line number in the source file:

  File "<fstring>", line 1
    (**kwargs)
      ^
SyntaxError: invalid syntax


This is the error message I would expect from the interpreter, but not when running a python script.   A demo script is as follows: 

    ''' f-string bug demonstration '''

    def main(*args, **kwargs):
        print(f"main() called with *args={*args}, **kwargs={**kwargs}")

With a longer python file, it is hard to find the offending line.
Should the line number be displayed in the error message?

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: python3 3.7.5-1
ProcVersionSignature: Ubuntu 5.3.0-46.38-generic 5.3.18
Uname: Linux 5.3.0-46-generic x86_64
ApportVersion: 2.20.11-0ubuntu8.8
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sat Apr 11 17:08:35 2020
SourcePackage: python3-defaults
UpgradeStatus: Upgraded to eoan on 2019-10-23 (170 days ago)

** Affects: python3-defaults (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug eoan

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https://bugs.launchpad.net/bugs/1872209

Title:
  syntax error message in f-string doesn't report line number

Status in python3-defaults package in Ubuntu:
  New

Bug description:
  I accidentally came across this annoying 'feature' or more likely,
  bug.

  The following code 
     f"...foo ... {**kwargs} ..."
  produces a very basic syntax error message with no line number in the source file:

    File "<fstring>", line 1
      (**kwargs)
        ^
  SyntaxError: invalid syntax

  
  This is the error message I would expect from the interpreter, but not when running a python script.   A demo script is as follows: 

      ''' f-string bug demonstration '''

      def main(*args, **kwargs):
          print(f"main() called with *args={*args}, **kwargs={**kwargs}")

  With a longer python file, it is hard to find the offending line.
  Should the line number be displayed in the error message?

  ProblemType: Bug
  DistroRelease: Ubuntu 19.10
  Package: python3 3.7.5-1
  ProcVersionSignature: Ubuntu 5.3.0-46.38-generic 5.3.18
  Uname: Linux 5.3.0-46-generic x86_64
  ApportVersion: 2.20.11-0ubuntu8.8
  Architecture: amd64
  CurrentDesktop: ubuntu:GNOME
  Date: Sat Apr 11 17:08:35 2020
  SourcePackage: python3-defaults
  UpgradeStatus: Upgraded to eoan on 2019-10-23 (170 days ago)

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