Added support for auth plugins.

httpie/plugins/base.py

@@ -0,0 +1,28 @@
+class AuthPlugin(object):
+    """
+    Base auth plugin class.
+
+    See <https://github.com/jkbr/httpie-ntlm> for an example auth plugin.
+
+    """
+
+    # The value that should be passed to --auth-type
+    # to use this auth plugin. Eg. "my-auth"
+    auth_type = None
+
+    # The name of the plugin, eg. "My auth".
+    name = None
+
+    # Optional short description. Will be be shown in the help
+    # under --auth-type.
+    description = None
+
+    # This be set automatically once the plugin has been loaded.
+    package_name = None
+
+    def get_auth(self, username, password):
+        """
+        Return a ``requests.auth.AuthBase`` subclass instance.
+
+        """
+        raise NotImplementedError()