set minimal veersion to 3.5

Author: echarles

.travis.yml

@@ -60,6 +60,8 @@ matrix:
           env: GROUP=python
         - python: 3.8
           env: GROUP=python
+        - python: 3.5
+          env: GROUP=docs
         - python: 3.6
           env: GROUP=docs
         - python: 3.7

setup.py

@@ -19,7 +19,7 @@
 name = "jupyter_server"
 
 # Minimal Python version sanity check
-if sys.version_info < (3,6):
+if sys.version_info < (3,5):
     error = "ERROR: %s requires Python version 3.5 or above." % name
     print(error, file=sys.stderr)
     sys.exit(1)