🚑 Exclude sphinx conf from pytest auto-discovery

But only under Python 3.5!

conftest.py

@@ -25,4 +25,5 @@ collect_ignore = [
 
 
 if sys.version_info < (3, 6):
+    collect_ignore.append('docs/conf.py')  # uses f-strings
     collect_ignore.append('pavement.py')