Drop install_command usage in tox

Use the default value provided by tox:

https://tox.readthedocs.io/en/latest/config.html#conf-install_command

See discussion on the openstack-discuss ML [1]
for the complete context.

Adjust the python-keystoneclient library requirement
to the minimum required by horizon.

[1] http://lists.openstack.org/pipermail/openstack-discuss/2020-April/014237.html

Change-Id: I6344f44fb955d631a4f0a13fa53ecc19826c7ea6
Signed-off-by: Goutham Pacha Ravi <gouthampravi@gmail.com>

lower-constraints.txt

@@ -72,10 +72,10 @@ pyparsing==2.2.0
 pyperclip==1.6.0
 pyScss==1.3.7
 pytest==5.3.5
-python-cinderclient==3.5.0
+python-cinderclient==5.0.0
 python-dateutil==2.7.0
 python-glanceclient==2.9.1
-python-keystoneclient==3.8.0
+python-keystoneclient==3.22.0
 python-manilaclient==1.29.0
 python-mimeparse==1.6.0
 python-neutronclient==6.7.0

requirements.txt

@@ -7,7 +7,7 @@ pbr!=2.1.0,>=2.0.0 # Apache-2.0
 django-compressor>=2.0 # MIT
 iso8601>=0.1.11 # MIT
 oslo.utils>=3.33.0 # Apache-2.0
-python-keystoneclient>=3.8.0 # Apache-2.0
+python-keystoneclient>=3.22.0 # Apache-2.0
 python-manilaclient>=1.29.0 # Apache-2.0
 
 horizon>=17.1.0  # Apache-2.0

tox.ini

@@ -5,7 +5,6 @@ skipsdist = True
 
 [testenv]
 basepython = python3
-install_command = pip install {opts} {packages}
 usedevelop = True
 setenv =
    VIRTUAL_ENV={envdir}