Add support to build api-ref as plain text

To be able to do that stanzas: "rest_method", "rest_expand_all" and
"http_code" are required for the "text" sphinx node visitor function.

Change-Id: Ib5e298dc0355886d1c373df1b82454390db8487a

os_api_ref/__init__.py

@@ -26,6 +26,7 @@ import yaml
 
 from os_api_ref.http_codes import http_code
 from os_api_ref.http_codes import http_code_html
+from os_api_ref.http_codes import http_code_text
 from os_api_ref.http_codes import HTTPResponseCodeDirective
 
 __version__ = pbr.version.VersionInfo(
@@ -555,6 +556,14 @@ def rest_expand_all_html(self, node):
     raise nodes.SkipNode
 
 
+def rest_method_text(self, node):
+    raise nodes.SkipNode
+
+
+def rest_expand_all_text(self, node):
+    raise nodes.SkipNode
+
+
 def create_mv_selector(node):
 
     mv_list = '<option value="" selected="selected">All</option>'
@@ -672,9 +681,12 @@ def setup(app):
     # TODO(sdague): if someone wants to support latex/pdf, or man page
     # generation using these stanzas, here is where you'd need to
     # specify content specific renderers.
-    app.add_node(rest_method, html=(rest_method_html, None))
-    app.add_node(rest_expand_all, html=(rest_expand_all_html, None))
-    app.add_node(http_code, html=(http_code_html, None))
+    app.add_node(rest_method, html=(rest_method_html, None),
+                 text=(rest_method_text, None))
+    app.add_node(rest_expand_all, html=(rest_expand_all_html, None),
+                 text=(rest_expand_all_text, None))
+    app.add_node(http_code, html=(http_code_html, None),
+                 text=(http_code_text, None))
 
     # This specifies all our directives that we're adding
     app.add_directive('rest_parameters', RestParametersDirective)

os_api_ref/http_codes.py

@@ -221,6 +221,10 @@ def http_code_html(self, node):
     raise nodes.SkipNode
 
 
+def http_code_text(self, node):
+    raise nodes.SkipNode
+
+
 class http_code(nodes.Part, nodes.Element):
     """Node for http_code stanza