Used isort to order all import statements

src/setup.cfg

@@ -3,3 +3,12 @@ ignore = N802,W503
 max-line-length = 160
 exclude = migrations,.ropeproject,static,mt940.py,_static
 max-complexity = 11
+
+[isort]
+combine_as_imports = true
+default_section = THIRDPARTY
+include_trailing_comma = true
+known_first_party = pretix
+multi_line_output = 5
+not_skip = __init__.py
+skip = make_testdata.py,wsgi.py,bootstrap