Avoid a full install in tox environments that do not need it

Usage of usedevelop=True results in all requirements.txt dependencies
always installed (without constraints) even when requirements.txt
is not explicitly added. Override usedevelop for these environments.

Add requirements.txt to the 'docs' environment since it imports
the whole ironic in the process.

Create a separate doc/requirements.txt.

Change-Id: I352f21772ccd68b35806f46851f254edb7c24c60

doc/requirements.txt

@@ -0,0 +1,6 @@
+os-api-ref>=1.4.0 # Apache-2.0
+reno>=3.1.0 # Apache-2.0
+sphinx>=2.0.0,!=2.1.0 # BSD
+sphinxcontrib-svg2pdfconverter>=0.1.0 # BSD
+sphinxcontrib-apidoc>=0.2.0  # BSD
+openstackdocstheme>=2.2.0 # Apache-2.0

test-requirements.txt

@@ -4,17 +4,7 @@
 
 bandit!=1.6.0,>=1.1.0,<2.0.0 # Apache-2.0
 coverage!=4.4,>=4.0 # Apache-2.0
-os-api-ref>=1.4.0 # Apache-2.0
 pymemcache!=1.3.0,>=1.2.9 # Apache-2.0
 stestr>=1.0.0 # Apache-2.0
 fixtures>=3.0.0 # Apache-2.0/BSD
 oslotest>=3.2.0 # Apache-2.0
-
-# DOC test requirements
-doc8>=0.6.0 # Apache-2.0
-reno>=3.1.0 # Apache-2.0
-sphinx>=2.0.0,!=2.1.0 # BSD
-sphinxcontrib-svg2pdfconverter>=0.1.0 # BSD
-sphinxcontrib-apidoc>=0.2.0  # BSD
-openstackdocstheme>=2.2.0 # Apache-2.0
-

tox.ini

@@ -1,5 +1,6 @@
 [tox]
 minversion = 3.2.1
+skipsdist = True
 envlist = py3,pep8,functional-py38
 ignore_basepython_conflict=true
 
@@ -23,11 +24,19 @@ passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
 commands = {posargs}
 
 [testenv:api-ref]
+usedevelop = False
+deps =
+    -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+    -r{toxinidir}/doc/requirements.txt
 whitelist_externals = bash
 commands =
   sphinx-build -W -b html -d api-ref/build/doctrees api-ref/source api-ref/build/html
 
 [testenv:releasenotes]
+usedevelop = False
+deps =
+    -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+    -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:cover]
@@ -42,6 +51,7 @@ commands =
     coverage html -d ./cover --omit='*test*'
 
 [testenv:pep8]
+usedevelop = False
 deps =
     flake8-import-order>=0.17.1 # LGPLv3
     hacking>=3.1.0,<4.0.0 # Apache-2.0
@@ -86,9 +96,11 @@ import_exceptions = ironic_inspector.common.i18n
 [testenv:docs]
 setenv = PYTHONHASHSEED=0
 sitepackages = False
+# NOTE(dtantsur): documentation building process requires importing ironic
 deps =
     -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
-    -r{toxinidir}/test-requirements.txt
+    -r{toxinidir}/requirements.txt
+    -r{toxinidir}/doc/requirements.txt
 commands =
   sphinx-build -W -b html doc/source doc/build/html
 
@@ -106,7 +118,10 @@ deps =
   -r{toxinidir}/requirements.txt
 
 [testenv:bandit]
-deps = -r{toxinidir}/test-requirements.txt
+usedevelop = False
+deps =
+    -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+    -r{toxinidir}/test-requirements.txt
 commands = bandit -r ironic_inspector -x test -n 5 -ll -c tools/bandit.yml
 
 # This environment can be used to quickly validate that all needed system