Fix used-before-assignment

Fix the following warning from the unit test:

onionbalance/_version.py:89:43: E0601: Using variable 'dispcmd' before
assignment (used-before-assignment)

requested review from @rhatto

assigned to @rhatto

changed the description

I have run tests manually and this change seems to work.

approved this merge request

merged

mentioned in commit 3d3db79e