ImportError while loading conftest '/build/sigal/src/sigal-2.2/tests/conftest.py'.
tests/conftest.py:8: in <module>
    from sigal import signals
sigal/__init__.py:33: in <module>
    from .gallery import Gallery
sigal/gallery.py:43: in <module>
    from . import image, signals, video
sigal/image.py:44: in <module>
    import pilkit.processors
E   ModuleNotFoundError: No module named 'pilkit'
==> ERROR: A failure occurred in check().
    Aborting...