Avoid tox-install.sh

Instead of using tox-install.sh, we can install horizon and neutron
now directly from pypi - or use the current branch in CI system using
tox-siblings.

Update tox.ini for this change and add neutron to requirements file.

Change-Id: Ib7d66460c21e3dbcf2d55d7ecac23315daa65ec7

requirements.txt

@@ -17,8 +17,4 @@ oslo.messaging>=5.29.0 # Apache-2.0
 oslo.serialization!=2.19.1,>=2.18.0 # Apache-2.0
 oslo.utils>=3.33.0 # Apache-2.0
 neutron-lib>=1.12.0 # Apache-2.0
-
-# This project does depend on neutron as a library, but the
-# openstack tooling does not play nicely with projects that
-# are not publicly available in pypi.
-# -e git+https://git.openstack.org/openstack/neutron#egg=neutron
+neutron>=12.0.0  # Apache-2.0

tox.ini

@@ -8,8 +8,9 @@ setenv = VIRTUAL_ENV={envdir}
          PYTHONWARNINGS=default::DeprecationWarning
 passenv = TRACE_FAILONLY
 usedevelop = True
-install_command = {toxinidir}/tools/tox_install.sh {env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
-deps = -r{toxinidir}/requirements.txt
+install_command = pip install {opts} {packages}
+deps = -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
+       -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 whitelist_externals =
     sh