Update docs requirements and fix link

- update documentation building requirement
- fix broken link in documentation page

Change-Id: I3b17aac420233b027acc14666fb50fdbd220b26d

doc/requirements.txt

@@ -5,5 +5,6 @@
 oslotest>=3.2.0               # Apache-2.0
 oslo.log>=3.36.0              # Apache-2.0
 reno>=2.5.0                   # Apache-2.0
-sphinx!=1.6.6,>=1.6.2         # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2;python_version>='3.4'         # BSD
 sphinx_rtd_theme>=0.4.2,< 1   # Apache-2.0

doc/source/index.rst

@@ -12,7 +12,7 @@ You can look for additional documentation also in the
 `OpenStack wiki <http://wiki.openstack.org/>`__.
 
 This documentation is generated by the Sphinx toolkit and lives in the `source
-tree <https://opendev.org/x/tobiko/doc/source>`__.
+tree <https://opendev.org/x/tobiko/src/branch/master/doc/source>`__.
 
 Enjoy!
 

tox.ini

@@ -142,27 +142,34 @@ commands = {posargs}
 
 # --- documentation environments ----------------------------------------------
 
-[testenv:docs]
+[docs]
 
 basepython = python3
 envdir = {toxworkdir}/docs
 deps = -r{toxinidir}/doc/requirements.txt
+
+
+[testenv:docs]
+
+basepython = {[docs]basepython}
+envdir = {[docs]envdir}
+deps = {[docs]deps}
 commands = sphinx-build -W -b html doc/source doc/build/html
 
 
 [testenv:linkcheck]
 
-basepython = python3
-envdir = {toxworkdir}/docs
-deps = {[testenv:docs]deps}
+basepython = {[docs]basepython}
+envdir = {[docs]envdir}
+deps = {[docs]deps}
 commands = sphinx-build -W -b linkcheck doc/source doc/build/linkcheck
 
 
 [testenv:releasenotes]
 
-basepython = python3
-envdir = {toxworkdir}/docs
-deps = {[testenv:docs]deps}
+basepython = {[docs]basepython}
+envdir = {[docs]envdir}
+deps = {[docs]deps}
 commands =
     sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html