Merge pull request #294 from rmarren1/no-layout-error

Error when no layout is present.

Author: rmarren1

Diff for: dash/dash.py

@@ -558,6 +558,15 @@ def dispatch(self):
         return self.callback_map[target_id]['callback'](*args)
 
     def _setup_server(self):
+        # Make sure `layout` is set before running the server
+        value = getattr(self, 'layout')
+        if value is None:
+            raise exceptions.NoLayoutException(
+                ''
+                'The layout was `None` '
+                'at the time that `run_server` was called. '
+                'Make sure to set the `layout` attribute of your application '
+                'before running the server.')
         self._generate_scripts_html()
         self._generate_css_dist_html()
 

Diff for: dash/exceptions.py

@@ -2,6 +2,10 @@ class DashException(Exception):
     pass
 
 
+class NoLayoutException(DashException):
+    pass
+
+
 class CallbackException(DashException):
     pass
 

Diff for: dev-requirements.txt

@@ -12,4 +12,4 @@ six
 plotly>=2.0.8
 requests[security]
 flake8
-pylint
+pylint==1.9.2