fix(.bashrc): prevent implicit usage of keyring for python

When using poetry I recently ran into an issue as described here:
 python-poetry/poetry#1917
It seems that the poetry authors enabled the automatic support of
 keyring. This does not check if keyring is actually used.

I decided to apply this fix here, since I think of poetry as a useful
 tool to steer my python projects. Maybe this is fixed within the next
 poetry release anyhow. Then I'll just remove it. Otherwise this fix is
 useful across this system, since I don't use keyring up to now that
 much. Worst case I can deactivate it on specific systems.

.bashrc

@@ -117,3 +117,6 @@ alias cfg='/usr/bin/git --git-dir=$HOME/.cfg/ --work-tree=$HOME'
 alias cfgedit='GIT_DIR=$HOME/.cfg GIT_WORK_TREE=$HOME vim'
 
 export PATH="$HOME/.local/bin:$PATH"
+
+# Prevent usage of Keyring within Poetry
+export PYTHON_KEYRING_BACKEND=keyring.backends.null.Keyring