WARNING: Writing cache to u'/home/dexpl/.cache/youtube-dl/youtube-sigfuncs/js_vflXGBaUN_82.json' failed: Traceback (most recent call last):

 "/bin/youtube-dl/youtube_dl/extractor/youtube.py", line 391, in _extract_signature_function
cache_res = res(test_string)

 "/bin/youtube-dl/youtube_dl/extractor/youtube.py", line 449, in <lambda>
return lambda s: initial_function([s])

 "/bin/youtube-dl/youtube_dl/jsinterp.py", line 113, in resf
res = self.interpret_statement(stmt, local_vars)

 "/bin/youtube-dl/youtube_dl/jsinterp.py", line 43, in interpret_statement
'Cannot determine left side of statement in %r' % stmt)ExtractorError: Cannot determine left side of statement in u'xh(this.j,a)'; please report this issue on https://yt-dl.org/bug . Be sure to call youtube-dl with the --verbose flag and include its complete output. Make sure you are using the latest version; type
youtube-dl -U
to update.
Traceback (most recent call last):

 "iris.py", line 11, in <module>
scatter(flowers["petal_length"], flowers["petal_width"], color=flowers["color"], fill_alpha=0.2, radius=5)

 "/Users/bryan/work/Bokeh/bokeh/plotting.py", line 738, in scatter
GlyphFunction(glyphclass, ("x", "y"))(*args, **kwargs)

 "/Users/bryan/work/Bokeh/bokeh/plotting.py", line 322, in wrapper
session.add(plot)AttributeError: 'NoneType' object has no attribute 'add'