's' is not a valid plotly symbol string, use 'circle' instead
'plasma' is not a valid plotly colorscale, use 'viridis' instead

The global plotly library object was renamed from 'Plotly' to '_Plotly'
in plotly.py 3.4.0 to avoid a naming conflict when a Jupyter Notebook
heading contained the text 'Plotly'

See:
plotly/plotly.py#816
plotly/plotly.py#1250

Graph objects are now structured hierarchically, so go.Marker was
deprecated in favor of go.layout.Marker.  The use of these classes
is fully optional, and they can be replaced by plain dict instances in
cases where local validation, tab completions, and docstrings aren't
needed.

cannot be mutated in place. Instead, the add_traces method is used
to append additional traces to the figure.

rather than lists so they cannot be extended in place.
The += operator can be used instead to replace the object array with
an extended version of itself.

dict instances with some dict-like methods. The to_plotly_json method
is used to convert a graph object into a Python dict.

… channel

but when loaded into the notebook it is loaded as _Plotly.

(before this commit figures rendered properly in the jupyter notebook
but an error was raised when output to an HTML file that _Plotly is
not defined)

… timeout.

See https://docs.travis-ci.com/user/common-build-problems/#build-times-out-because-no-output-was-received

Prior intermittent CI error:
```
...
$ conda env update -n holoviews -q -f environment.yml
Solving environment: ...working... done
Preparing transaction: ...working... done
Verifying transaction: ...working... done
Executing transaction: ...working... dbus post-link :: /etc/machine-id not found ..
dbus post-link :: .. using /proc/sys/kernel/random/boot_id
No output has been received in the last 10m0s, this potentially indicates a stalled build or something wrong with the build itself.
```