Fix subcommand aliases set in namespace instead of the subcommand name - #978

Check warning on line 137 in jsonargparse_tests/test_subcommands.py

sonarqubecloud / SonarCloud Code Analysis

Refactor this exception test to have only one invocation possibly throwing an exception.

See more on https://sonarcloud.io/project/issues?id=mauvilsa_jsonargparse&issues=AaCrwstdSxzUcpQ1zB8A&open=AaCrwstdSxzUcpQ1zB8A&pullRequest=978