curtin.readthedocs.io missing ToC and proper theme

[Bruce Elrick]

The built html docs at https://curtin.readthedocs.io/ (redirects to
https://curtin.readthedocs.io/en/latest/) have a truncated table of contents in the left-side
navigation. Further, the HTML theming does not match the RTD standard.

In comparison, locally-built docs have a correct ToC navigation on the left side and match the
RTD theme.

The problem appears to be this code in doc/conf.py:

# on_rtd is whether we are on readthedocs.org, this line of code grabbed from
# docs.readthedocs.org
on_rtd = os.environ.get('READTHEDOCS', None) == 'True'

if not on_rtd: # only import and set the theme if we're building docs locally
    import sphinx_rtd_theme
    html_theme = 'sphinx_rtd_theme'
    html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]

# otherwise, readthedocs.org uses their theme by default, so no need to specify
# it

perhaps the RTD automatic theming used to work but no longer does.

I've tested the following change:

------
$ git diff master
diff --git a/doc/conf.py b/doc/conf.py
index d7a38ff5..fc0cd347 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -96,19 +96,15 @@ pygments_style = 'sphinx'

 # The theme to use for HTML and HTML Help pages. See the documentation for
 # a list of builtin themes.
-html_theme = 'classic'
+#html_theme = 'classic'

 # on_rtd is whether we are on readthedocs.org, this line of code grabbed from
 # docs.readthedocs.org
-on_rtd = os.environ.get('READTHEDOCS', None) == 'True'
+#on_rtd = os.environ.get('READTHEDOCS', None) == 'True'

-if not on_rtd: # only import and set the theme if we're building docs locally
- import sphinx_rtd_theme
- html_theme = 'sphinx_rtd_theme'
- html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
-
-# otherwise, readthedocs.org uses their theme by default, so no need to specify
-# it
+import sphinx_rtd_theme
+html_theme = 'sphinx_rtd_theme'
+html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]

 # Theme options are theme-specific and customize the look and feel of a theme
 # further. For a list of options available for each theme, see the
------

by connecting it to the following RTD project:
https://virtuous-sloth-curtin-docs.readthedocs.io/en/latest/

[Bruce Elrick (virtuous-sloth)]

A GitHub PR https://github.com/canonical/curtin/pull/7 has been created (I'm not sure which is
the primary code repository, the github one or the one hosted here).

[Bruce Elrick (virtuous-sloth)]

I now see that you are using the LP git repo. I created an [LP MP](https://code.launchpad.net/~virtuous-sloth/curtin/+git/curtin/+merge/441502)