lektor build error on website

Traceback (most recent call last):
  File "/usr/local/bin/lektor", line 11, in <module>
    sys.exit(main())
  File "/usr/local/lib/lektor/lib/python2.7/site-packages/click/core.py", line 716, in __call__
    return self.main(*args, **kwargs)
  File "/usr/local/lib/lektor/lib/python2.7/site-packages/click/core.py", line 696, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/lektor/lib/python2.7/site-packages/click/core.py", line 1060, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/lektor/lib/python2.7/site-packages/click/core.py", line 889, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/lib/lektor/lib/python2.7/site-packages/click/core.py", line 534, in invoke
    return callback(*args, **kwargs)
  File "/usr/local/lib/lektor/lib/python2.7/site-packages/click/decorators.py", line 64, in new_func
    return ctx.invoke(f, obj, *args[1:], **kwargs)
  File "/usr/local/lib/lektor/lib/python2.7/site-packages/click/core.py", line 534, in invoke
    return callback(*args, **kwargs)
  File "/usr/local/lib/lektor/lib/python2.7/site-packages/lektor/cli.py", line 159, in build_cmd
    ctx.load_plugins()
  File "/usr/local/lib/lektor/lib/python2.7/site-packages/lektor/cli.py", line 84, in load_plugins
    initialize_plugins(self.get_env())
  File "/usr/local/lib/lektor/lib/python2.7/site-packages/lektor/pluginsystem.py", line 121, in initialize_plugins
    plugins = load_plugins()
  File "/usr/local/lib/lektor/lib/python2.7/site-packages/lektor/pluginsystem.py", line 115, in load_plugins
    rv[ep.name] = ep.load()
  File "/usr/local/lib/lektor/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2202, in load
    return self.resolve()
  File "/usr/local/lib/lektor/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2208, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "/Users/nfunnell/Library/Caches/Lektor/packages/d47d43d85b5e12448e9c09ccaf7214ac/lektor_atom.py", line 14, in <module>
    from lektor.utils import build_url
ImportError: cannot import name build_url