Update Semaphore configuration

Author: awolfden

.semaphore/semaphore.yml

@@ -13,6 +13,7 @@ blocks:
             - sem-version python 3.8
             - 'flake8 . --count --select=E9,F7,F82 --show-source --statistics'
             - flake8 . --count --exit-zero --max-complexity=10 --statistics
+            - black --check .
       prologue:
         commands:
           - checkout