add flake8-isort, with a caveat

tox.ini

@@ -46,10 +46,11 @@ deps =
     flake8-builtins
     flake8-docstrings
     flake8-executable
+    flake8-isort
     flake8-logging-format
 commands =
     flake8
-    - flake8 --disable-noqa --select=E,W,F,C,D,A,G,B
+    - flake8 --disable-noqa --select=E,W,F,C,D,A,G,B,I
 
 [coverage:paths]
 source =
@@ -70,6 +71,12 @@ exclude =
     instance/
 max-complexity = 10
 
+[isort]
+line_length = 120
+# only way I could figure out how to make tests/conftest.py happy and have pytest separate from incorporealcms
+# and if I let them be combined in tox runs, flake8-isort in vim would complain :(
+forced_separate = incorporealcms
+
 [pytest]
 python_files =
     *_tests.py