Traceback (most recent call last):
  File "/build/python-pafy/src/pafy-0.5.5/pafy/pafy.py", line 48, in <module>
    import youtube_dl
ModuleNotFoundError: No module named 'youtube_dl'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/build/python-pafy/src/pafy-0.5.5/setup.py", line 13, in <module>
    from pafy import __version__
  File "/build/python-pafy/src/pafy-0.5.5/pafy/__init__.py", line 7, in <module>
    from .pafy import new
  File "/build/python-pafy/src/pafy-0.5.5/pafy/pafy.py", line 51, in <module>
    raise ImportError(
ImportError: pafy: youtube-dl not found; you can use the internal backend by setting the environmental variable PAFY_BACKEND to "internal". It is not enabled by default because it is not as well maintained as the youtube-dl backend.
==> ERROR: A failure occurred in package_python-pafy().
    Aborting...