In order to accomodate installation in parallel with ZeroMQ components built
without draft socket support, the ZeroMQ draft components have been installed
under a unique prefix. The installation may be described with the pkgconfig file
installed within this prefix.

The pathnames for the draft installation may be illustrated in the following, 
using an amd64 library dir as the draft component prefix.

- libdir:  /usr/lib64/zmq-draft
- includedir:  /usr/lib64/zmq-draft/include
- pkg config path: /usr/lib64/zmq-draft/pkgconfig

Given a single machine architecture, the exact installation pathanames may be
determined using the rpm shell command.

$ rpm -ql zeromq-devel-draft
/usr/lib64/zmq-draft                                                               
/usr/lib64/zmq-draft/include                                                       
/usr/lib64/zmq-draft/include/zmq.h                                                 
/usr/lib64/zmq-draft/include/zmq_utils.h                                           
/usr/lib64/zmq-draft/libzmq.so                                                     
/usr/lib64/zmq-draft/pkgconfig                                                     
/usr/lib64/zmq-draft/pkgconfig/libzmq.pc 
...

For example, pyzmq can be installed as linked to the draft libraries,
using the following shell command.

env ZMQ_DRAFT_API=1 \
 PKG_CONFIG_PATHS=/usr/lib64/zmq-draft/pkgconfig:/usr/lib/pkgconfig \
 pip install -v pyzmq --no-binary pyzmq --no-cache --force pyzmq

The installation can be tested with pyzmq using the following, such that 
should evaluate without error.

 python3 -m zmq.tests.test_draft \
  -c 'test = TestDraftSockets(); test.test_client_server(); test.test_radio_dish()'
