Error message:
Traceback (most recent call last):
  File "./ntpclients/ntpmon", line 66, in <module>
    sys.stderr.write(usage)
NameError: name 'usage' is not defined

Upstream waf fixed an incompatibility with Python 2.6.4 related to the
subprocess module and multiple AttributeException being thrown.

See https://github.com/waf-project/waf/issues/1874 for additional information

Fixes GitLab issue #198

Reverts "Change pre-requisites to indicate Python 2 must be at 2.6.6 or later."

Leftover cleanup from "Address GitLab issue #197: ntpq and packet.py require
python2.7+"

pyflakes reported:
pylib/packet.py:934: local variable 'msg' is assigned to but never used
pylib/packet.py:961: local variable 'reason' is assigned to but never used

Also document long options in the synopsis