Mixing POETRY_HTTP_BASIC_ env vars with CLI args does not work on poetry publish

• I am on the latest Poetry version.
• I have searched the issues of this repo and believe that this is not a duplicate.
• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS version and name: Debian
• Poetry version: 1.1.13

Issue

poetry publish does not consider --username when supplied as a standalone CLI argument (i.e without --password).

Env vars only ✔️

poetry config repositories.myrepo $REPO_URL \
  && POETRY_HTTP_BASIC_MYREPO_USERNAME=$USERNAME \
     POETRY_HTTP_BASIC_MYREPO_PASSWORD=$PASSWORD \
     poetry publish -r myrepo

CLI args only ✔️

poetry config repositories.myrepo $REPO_URL \
  && poetry publish -r myrepo -u $USERNAME -p $PASSWORD

Mixed ❌

poetry config repositories.myrepo $REPO_URL \
  && POETRY_HTTP_BASIC_MYREPO_PASSWORD=$PASSWORD \
     poetry publish -r myrepo -u $USERNAME

No suitable keyring backends were found
Using a plaintext file to store and retrieve credentials
Username: 
  RuntimeError
  Aborted

This issue is particularly easy to work around, however still got me off-guard, as I expected that environment variables can be mixed with CLI args.