Attempted fix for PyCurl installation issue plus correspondingly updated documentation.

Author: krinsman

README.md

@@ -84,7 +84,7 @@ $ docker-compose up
 
 ### Local Installation
 
-The Notebook Viewer requires several binary packages to be installed on your system. The primary ones are `libmemcached-dev libcurl4-openssl-dev pandoc libevent-dev`. Package names may differ on your system, see [salt-states](https://github.com/rgbkrk/salt-states-nbviewer/blob/master/nbviewer/init.sls) for more details.
+The Notebook Viewer requires several binary packages to be installed on your system. The primary ones are `libmemcached-dev libcurl4-openssl-dev pandoc libevent-dev libgnutls28-dev`. Package names may differ on your system, see [salt-states](https://github.com/rgbkrk/salt-states-nbviewer/blob/master/nbviewer/init.sls) for more details.
 
 If they are installed, you can install the required Python packages via pip.
 

nbviewer/handlers.py

@@ -76,16 +76,18 @@ def get_provider_rewrites(self):
 #-----------------------------------------------------------------------------
 
 def format_handlers(formats, urlspecs, **handler_settings):
+    """
+    Tornado handler URLSpec of form (route, handler_class, initalize_kwargs)
+    https://www.tornadoweb.org/en/stable/web.html#tornado.web.URLSpec
+    kwargs passed to initialize are None by default but can be added
+    https://www.tornadoweb.org/en/stable/web.html#tornado.web.RequestHandler.initialize
+    """
     urlspecs = [
         (prefix + url, handler, {
             "format": format,
             "format_prefix": prefix
         })
         for format in formats
-        # Tornado handler URLSpec of form (route, handler_class, initalize_kwargs)
-        # https://www.tornadoweb.org/en/stable/web.html#tornado.web.URLSpec
-        # kwargs passed to initialize are None by default but can be added
-        # https://www.tornadoweb.org/en/stable/web.html#tornado.web.RequestHandler.initialize
         for url, handler, initialize_kwargs in urlspecs
         for prefix in [format_prefix + format]
     ]
@@ -98,12 +100,14 @@ def format_handlers(formats, urlspecs, **handler_settings):
     return urlspecs
 
 def init_handlers(formats, providers, base_url, localfiles, **handler_kwargs):
-    # `handler_kwargs` is a dict of dicts: first dict is `handler_names`, which
-    # specifies the handler_classes to load for the providers, the second
-    # is `handler_settings` (see comments in format_handlers)
-    # Only `handler_settings` should get added to the initialize_kwargs in the
-    # handler URLSpecs, which is why we pass only it to `format_handlers`
-    # but both it and `handler_names` to `provider_handlers`
+    """
+    `handler_kwargs` is a dict of dicts: first dict is `handler_names`, which
+    specifies the handler_classes to load for the providers, the second
+    is `handler_settings` (see comments in format_handlers)
+    Only `handler_settings` should get added to the initialize_kwargs in the
+    handler URLSpecs, which is why we pass only it to `format_handlers`
+    but both it and `handler_names` to `provider_handlers`
+    """
     handler_settings = handler_kwargs['handler_settings']
 
     pre_providers = [

nbviewer/providers/__init__.py

@@ -20,10 +20,11 @@ def provider_handlers(providers, **handler_kwargs):
        augmented list of handlers: this allows the addition of, for
        example, custom URLs which should be intercepted before being
        handed to the basic `url` handler
+
+      `handler_kwargs` is a dict of dicts: first dict is `handler_names`, which
+      specifies the handler_classes to load for the providers, the second
+      is `handler_settings` (see comments in `format_handlers` in nbviewer/handlers.py)
     """
-    # `handler_kwargs` is a dict of dicts: first dict is `handler_names`, which
-    # specifies the handler_classes to load for the providers, the second
-    # is `handler_settings` (see comments in `format_handlers` in nbviewer/handlers.py)
     handler_names = handler_kwargs['handler_names']
     handler_settings = handler_kwargs['handler_settings']
 
@@ -56,8 +57,9 @@ def _load_provider_feature(feature, providers, **handler_names):
 
        The feature will be passed a list of feature implementations and must
        return that list, suitably modified.
+
+      `handler_names` is the same as the `handler_names` attribute of the NBViewer class
     """
-    # `handler_names` is the same as the `handler_names` attribute of the NBViewer class
 
     # Ex: provider = 'nbviewer.providers.url' 
     # provider.rsplit(',', 1) = ['nbviewer.providers', 'url']