Always use constraints

This flips the tox.ini to always use constraints installation for all
targets. It drops the extra -constraints targets in the process. This
makes it so there is no developer change required to operate in our new
world order.

Note that coverage and release-notes jobs cannot use constraints yet to
limitations of the tools we use. So, they continue to use the normal
non-constraint install.

Conflicts:
        tox.ini

Change-Id: I218f16c585b7b8a9ea73c6cf1c5b0aef2dcde015
Depends-On: Ia08c15914d9dbfc3f5dc04ca69a7be26efb6fe64
(cherry picked from commit 00a01d012c)

tox.ini

@@ -6,16 +6,17 @@ skipsdist = True
 [testenv]
 setenv = VIRTUAL_ENV={envdir}
 usedevelop = True
-install_command = pip install -U {opts} {packages}
+install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
 deps = -r{toxinidir}/test-requirements.txt
 commands = lockutils-wrapper python setup.py testr --slowest --testr-args='{posargs}'
 whitelist_externals = bash
 passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
 
-[tox:jenkins]
-downloadcache = ~/cache/pip
-
 [testenv:releasenotes]
+# NOTE(jaegerandi): this target does not use constraints because
+# upstream infra does not yet support it. Once that's fixed, we can
+# drop the install_command.
+install_command = pip install -U --force-reinstall {opts} {packages}
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:py34]
@@ -54,6 +55,10 @@ commands =
   bash -c "find glance -type f -regex '.*\.pot?' -print0|xargs -0 -n 1 msgfmt --check-format -o /dev/null"
 
 [testenv:cover]
+# NOTE(jaegerandi): this target does not use constraints because
+# upstream infra does not yet support it. Once that's fixed, we can
+# drop the install_command.
+install_command = pip install -U --force-reinstall {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
 commands = python setup.py testr --coverage --testr-args='^(?!.*test.*coverage).*$'