Install deps from wheelhouse

To make the charm install properly from behind a proxy and to
make it consistent with other python requirements, install
'keystoneauth1', 'python-glanceclient' from the wheelhouse. This
is how it was originally done but was changed to work around
layer basic issue #149 *1. This change reverts the workaround and
pins setuptools. In the longer term *2 will remove the needs
for the setuptools pinning.

*1 https://github.com/juju-solutions/layer-basic/issues/149
*2 https://github.com/juju-solutions/layer-basic/pull/156

Closes-Bug: #1855766

Change-Id: Ifc750a5a1ee8441bb5296fc0059fe90932c5b3cd
(cherry picked from commit ffc9774544)

src/layer.yaml

@@ -10,9 +10,6 @@ options:
     use_venv: True
     include_system_packages: False
     packages: [ 'libffi-dev', 'libssl-dev' ]
-    # python_packages replaces using src/wheelhouse.txt till
-    # layer-basic issues #149 is resolved.
-    python_packages: [ 'keystoneauth1', 'python-glanceclient' ]
   snap:
     octavia-diskimage-retrofit:
       channel: beta

src/wheelhouse.txt

@@ -1,2 +1,11 @@
-
 git+https://opendev.org/openstack/charms.openstack.git@stable/20.02#egg=charms.openstack
+keystoneauth1
+python-glanceclient
+# python-zipp 2.x introduces a requirement for setuptools 42.x which is not available.
+# resolve conflict:
+# layer-basic requires setuptools<42, zipp>=2.0.0 requires setuptools>42
+# LP: #1862186
+zipp < 2.0.0
+# Pin setuptools as tactical fix for LP: 1855766. Can be removed when
+# https://github.com/juju-solutions/layer-basic/issues/149 is fixed
+setuptools < 42.0.0