reinstate isort requirement, prior to py3.7 only

alexcjohnson · alexcjohnson · commit ec35ca641980 · 2020-12-16T14:02:14.000-05:00
diff --git a/requires-dev.txt b/requires-dev.txt
@@ -1,5 +1,6 @@
 dash_flow_example==0.0.5
 dash-dangerously-set-inner-html
+isort==4.3.21;python_version<"3.7"
 mock==4.0.3;python_version>="3.0"
 mock==3.0.5;python_version=="2.7"
 flake8==3.8.4
