Update docs building

Update docs building:
* Switch to sphinx-build
* Update requirements for Sphinx and openstackdocstheme for
  python 3, create doc/requirements.txt file.
* Remove unneeded doc and translation sections from setup.cfg
* Remove install_command, it's unneeded, the default is fine.
* Use TOX_CONSTRAINTS instead of obsolete UPPER_CONSTRAINTS

Change-Id: I6ff4427014fc967a6f7b28fc6cbe5a0f4eca601c
diff --git a/doc/requirements.txt b/doc/requirements.txt
new file mode 100644
index 0000000..72d01e9
--- /dev/null
+++ b/doc/requirements.txt
@@ -0,0 +1,4 @@
+sphinx>=2.0.0,!=2.1.0 # BSD
+openstackdocstheme>=2.0.0 # Apache-2.0
+
+reno>=2.5.0 # Apache-2.0
diff --git a/setup.cfg b/setup.cfg
index 241739d..e6277e3 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -24,11 +24,3 @@
 [entry_points]
 tempest.test_plugins =
     ironic_tests = ironic_tempest_plugin.plugin:IronicTempestPlugin
-
-[build_sphinx]
-source-dir = doc/source
-build-dir = doc/build
-all_files = 1
-
-[upload_sphinx]
-upload-dir = doc/build/html
diff --git a/test-requirements.txt b/test-requirements.txt
index 682db80..7e4adb2 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -7,8 +7,3 @@
 stestr>=1.0.0 # Apache-2.0
 coverage!=4.4,>=4.0 # Apache-2.0
 flake8-import-order>=0.17.1 # LGPLv3
-
-sphinx!=1.6.6,!=1.6.7,>=1.6.2 # BSD
-openstackdocstheme>=1.20.0 # Apache-2.0
-
-reno>=2.5.0 # Apache-2.0
diff --git a/tox.ini b/tox.ini
index 0f5ad24..28ac9e7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -7,11 +7,10 @@
 [testenv]
 basepython = python3
 usedevelop = True
-install_command = pip install {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
    PYTHONWARNINGS=default::DeprecationWarning
-deps = -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+deps = -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
        -r{toxinidir}/test-requirements.txt
 commands = stestr run --slowest {posargs}
 
@@ -32,9 +31,12 @@
     coverage xml -o cover/coverage.xml
 
 [testenv:docs]
-commands = python setup.py build_sphinx
+deps = -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+       -r{toxinidir}/doc/requirements.txt
+commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:pdf-docs]
+deps = {[testenv:docs]deps}
 whitelist_externals = make
 commands = sphinx-build -b latex doc/source doc/build/pdf
            make -C doc/build/pdf