Recibo el siguiente mensaje de error cuando intento configurar un entorno virtual con virtualenv 15.0.2 pero recibo el error de la rueda de herramientas de configuración de OSError con el código de error 1.

New python executable in /Users/nathmorissette/projects/tutorial/venv/bin/python
Installing setuptools, pip, wheel...
  Complete output from command /Users/nathmorissett...rial/venv/bin/python - setuptools pip wheel:
  Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
  File "/Users/nathmorissette/miniconda2/lib/python2.7/tempfile.py", line 32, in <module>
    import io as _io
  File "/Users/nathmorissette/miniconda2/lib/python2.7/io.py", line 51, in <module>
    import _io
ImportError: dlopen(/Users/nathmorissette/projects/tutorial/venv/lib/python2.7/lib-dynload/_io.so, 2): Symbol not found: __PyCodecInfo_GetIncrementalDecoder
  Referenced from: /Users/nathmorissette/projects/tutorial/venv/lib/python2.7/lib-dynload/_io.so
  Expected in: dynamic lookup

----------------------------------------
...Installing setuptools, pip, wheel...done.
Traceback (most recent call last):
  File "/Users/nathmorissette/miniconda2/bin/virtualenv", line 9, in <module>
    load_entry_point('virtualenv==15.0.2', 'console_scripts', 'virtualenv')()
  File "/Users/nathmorissette/miniconda2/lib/python2.7/site-packages/virtualenv-15.0.2-py2.7.egg/virtualenv.py", line 711, in main
    symlink=options.symlink)
  File "/Users/nathmorissette/miniconda2/lib/python2.7/site-packages/virtualenv-15.0.2-py2.7.egg/virtualenv.py", line 944, in create_environment
    download=download,
  File "/Users/nathmorissette/miniconda2/lib/python2.7/site-packages/virtualenv-15.0.2-py2.7.egg/virtualenv.py", line 900, in install_wheel
    call_subprocess(cmd, show_stdout=False, extra_env=env, stdin=SCRIPT)
  File "/Users/nathmorissette/miniconda2/lib/python2.7/site-packages/virtualenv-15.0.2-py2.7.egg/virtualenv.py", line 795, in call_subprocess
    % (cmd_desc, proc.returncode))
OSError: Command /Users/nathmorissett...rial/venv/bin/python - setuptools pip wheel failed with error code 1

¿Alguna idea de cómo resolver este problema?