Support Python 3.5 and add explicit python_requires metadata

Author: jonmmease

conda.recipe/meta.yaml

@@ -23,7 +23,7 @@ requirements:
     - jupyterlab=2.0
 
   run:
-    - python
+    - python>=3.5
     {% for dep in sdata.get('install_requires',{}) %}
     - {{ dep }}
     {% endfor %}

jupyter_dash/jupyter_app.py

@@ -210,7 +210,7 @@ def run_server(
             if JupyterDash.default_server_url:
                 server_url = JupyterDash.default_server_url.rstrip('/')
             else:
-                server_url = f'http://{host}:{port}'
+                server_url = 'http://{host}:{port}'.format(host=host, port=port)
         else:
             server_url = self.server_url.rstrip('/')
 

setup.py

@@ -134,6 +134,7 @@ def readme():
             "labextension/package.json",
         ],
     },
+    python_requires=">=3.5",
     data_files=[
         # like `jupyter nbextension install --sys-prefix`
         ("share/jupyter/nbextensions/jupyter_dash", [