[pgadmin-support] Building pgadmin4-1.1: Python3 virtual wrapper

Running Slackware-14.1/32-bit on the server with python-2.7.13 and
python3-3.5.2.
  As root I try to install the virtual environment and wrapper. The former
is installed; the latter not:

# pip3 install virtualenv virtualenv-wrapper
Collecting virtualenv  Downloading virtualenv-15.1.0-py2.py3-none-any.whl (1.8MB)    100%
|████████████████████████████████|1.8MB 236kB/s 
 
Collecting virtualenv-wrapper  Could not find a version that satisfies the requirement virtualenv-wrapper
(from versions: )
No matching distribution found for virtualenv-wrapper
  Can you offer a suggestion to resolve this? I can ask on the python mail
list if that's more appropriate.

Rich