Using custom braces in message template does not work · pylint-dev/pylint challenge

Problem statement

Bug description

Have any list of errors:

On pylint 1.7 w/ python3.6 - I am able to use this as my message template

$ pylint test.py --msg-template='{{ "Category": "{category}" }}'
No config file found, using default configuration
************* Module [redacted].test
{ "Category": "convention" }
{ "Category": "error" }
{ "Category": "error" }
{ "Category": "convention" }
{ "Category": "convention" }
{ "Category": "convention" }
{ "Category": "error" }

However, on Python3.9 with Pylint 2.12.2, I get the following:

$ pylint test.py --msg-template='{{ "Category": "{category}" }}'
[redacted]/site-packages/pylint/reporters/text.py:206: UserWarning: Don't recognize the argument '{ "Category"' in the --msg-template. Are you sure it is supported on the current version of pylint?
  warnings.warn(
************* Module [redacted].test
" }
" }
" }
" }
" }
" }

Is this intentional or a bug?

Configuration

_No response_

Command used

shell

pylint test.py --msg-template='{{ "Category": "{category}" }}'

Pylint output

shell

[redacted]/site-packages/pylint/reporters/text.py:206: UserWarning: Don't recognize the argument '{ "Category"' in the --msg-template. Are you sure it is supported on the current version of pylint?
  warnings.warn(
************* Module [redacted].test
" }
" }
" }
" }
" }
" }

Expected behavior

Expect the dictionary to print out with "Category" as the key.

Pylint version

shell

Affected Version:
pylint 2.12.2
astroid 2.9.2
Python 3.9.9+ (heads/3.9-dirty:a2295a4, Dec 21 2021, 22:32:52) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-44)]


Previously working version:
No config file found, using default configuration
pylint 1.7.4, 
astroid 1.6.6
Python 3.6.8 (default, Nov 16 2020, 16:55:22) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-44)]

OS / Environment

_No response_

Additional dependencies

_No response_

The environment starts at commit e90702074e68 (pylint-dev/pylint 2.15), dependencies installed and tests runnable from the first minute. You are graded by hidden tests taken from the fix that was actually merged upstream.