Add task for checking formatting

tasks.py

@@ -37,6 +37,12 @@ def fmt(c):
         print("Uncommitted change exist; skipping commit")
 
 
+@task
+def checkfmt(c):
+    """Automatically format the source code, committing it if it is safe to do so."""
+    return c.run("poetry run black --check $(find . -name '*.py')")
+
+
 @task
 def populate(c):
     """Populate the test database with fake-ish data"""