[stable-only] Fix sphinx doc jobqueens-eol

This is a combination of 2 commits to fix gate failure due to recent
failure of build-sphinx-docs-job since python 2 was replaced in it to
python 3.

1. tox: Make everything work with Python 3

Nothing too fancy here except that we've to work around a really ugly
side-effect of blockdiag.

Conflicts:
  tox.ini

Change-Id: Ibd32d30aacae65702d0ccbdb8a02b1667ec4e8ee
(cherry picked from commit b862f6ff35d1611d0d63623a6254fc889012bfb9)

2. Python 3 fix for sphinx doc

In Python 3, dict methods dict.keys() return “views” instead of lists.
Therefore, the code:

    impls = sorted(matrix.targets.keys())
    impls.sort()

should be replaced by:

    impls = sorted(matrix.targets.keys())

to be Python 3 compatible.

Change-Id: I50477b0ac43adff9e9b0220bd7c48d6ebb6471b3
(cherry picked from commit 8ca01a3abbeb088cab618e856e1d3cddfc5f0d35)

3 files changed, 15 insertions, 7 deletions

diff --git a/doc/ext/feature_matrix.py b/doc/ext/feature_matrix.py
index 16577509bc..4934e5894f 100644
--- a/doc/ext/feature_matrix.py
+++ b/doc/ext/feature_matrix.py
@@ -337,8 +337,7 @@ class FeatureMatrixDirective(rst.Directive):
         summaryhead.append(header)
 
         # then one column for each hypervisor driver
-        impls = matrix.targets.keys()
-        impls.sort()
+        impls = sorted(matrix.targets.keys())
         for key in impls:
             target = matrix.targets[key]
             implcol = nodes.entry()
@@ -378,8 +377,7 @@ class FeatureMatrixDirective(rst.Directive):
                 classes=["fm_maturity_" + feature.maturity]))
 
             # and then one column for each hypervisor driver
-            impls = matrix.targets.keys()
-            impls.sort()
+            impls = sorted(matrix.targets.keys())
             for key in impls:
                 target = matrix.targets[key]
                 impl = feature.implementations[key]
diff --git a/doc/source/conf.py b/doc/source/conf.py
index 2d5ccc0d77..61d4850405 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -181,13 +181,26 @@ def monkey_patch_blockdiag():
     text width rather than on word boundaries. There's a patch submitted to
     resolve this [1]_ but it's unlikely to merge anytime soon.
 
+    In addition, blockdiag monkey patches a core library function,
+    ``codecs.getreader`` [2]_, to work around some Python 3 issues. Because
+    this operates in the same environment as other code that uses this library,
+    it ends up causing issues elsewhere. We undo these destructive changes
+    pending a fix.
+
     TODO: Remove this once blockdiag is bumped to 1.6, which will hopefully
     include the fix.
 
     .. [1] https://bitbucket.org/blockdiag/blockdiag/pull-requests/16/
+    .. [2] https://bitbucket.org/blockdiag/blockdiag/src/1.5.3/src/blockdiag/utils/compat.py # noqa
     """
+    import codecs
+    from codecs import getreader
+
     from blockdiag.imagedraw import textfolder
 
+    # oh, blockdiag. Let's undo the mess you made.
+    codecs.getreader = getreader
+
     def splitlabel(text):
         """Split text to lines as generator.
 
diff --git a/tox.ini b/tox.ini
index 983baeb0ed..b3e0794bba 100644
--- a/tox.ini
+++ b/tox.ini
@@ -142,9 +142,6 @@ commands =
 commands = {posargs}
 
 [testenv:docs]
-# TODO(melwitt): This can be removed when the docs target can be run
-# with python 3.x
-basepython = python2.7
 commands =
   rm -rf doc/source/api doc/build api-guide/build api-ref/build placement-api-ref/build
   python setup.py build_sphinx