Use encoded URL when redirecting user notebooks

Otherwise it breaks for usernames that have url unsafe
characters.

jupyterhub/handlers/pages.py

@@ -8,7 +8,7 @@ from tornado import web, gen
 from .. import orm
 from ..utils import admin_only, url_path_join
 from .base import BaseHandler
-from .login import LoginHandler
+from urllib.parse import quote
 
 
 class RootHandler(BaseHandler):
@@ -75,7 +75,9 @@ class SpawnHandler(BaseHandler):
             self.finish(self._render_form())
         else:
             # not running, no form. Trigger spawn.
-            url = url_path_join(self.base_url, 'user', user.name)
+            # Creating the URL manually since the server does not
+            # exist yet
+            url = url_path_join(self.base_url, 'user', quote(user.name))
             self.redirect(url)
 
     @web.authenticated

share/jupyter/hub/templates/home.html

@@ -10,7 +10,7 @@
       {% endif %}
       <a id="start" class="btn btn-lg btn-success"
       {% if user.running %}
-        href="{{base_url}}user/{{user.name}}/"
+        href="{{ user.server.base_url }}"
       {% else %}
         href="{{base_url}}spawn"
       {% endif %}