2.7.2 and virtualenv

I am unable to create a jython 2.7.2 virtualenv. Performing a pip
install of virtualenv completes successfully. Executing from my jython's
bin directory:

  $ ./virtualenv -h

results in:

  /private/tmp/jy2.7.2/Lib/site-packages/filelock.py:451: UserWarning:
  only soft file lock is available warnings.warn("only soft file lock is
  available")

  RuntimeError: No virtualenv implementation for
  PythonInfo(spec=Jython2.7.2.final.0-32,
  exe=/private/tmp/jy2.7.2/bin/jython, platform=java1.8.0_181,
  version=u'2.7.2 (v2.7.2:925a3cc3b49d, Mar 21 2020, 10:03:58)\n[Java
  HotSpot(TM) 64-Bit Server VM (Oracle Corporation)]',
  encoding_fs_io=utf-8-UTF-8)

I receive similar results for:

  $ ./jython -m virtualenv -h

Environment details:

  $ ./jython --version
  Jython 2.7.2

  $ sw_vers
  ProductName:    Mac OS X
  ProductVersion: 10.14.6
  BuildVersion:   18G4032

My searching has come up empty, so I figure I must be missing something
obvious.