Log message:
py-plotly: add missing TOOL_DEPENDS

TODO: there's a config file in the PLIST that should be handled
with CONF_FILES

Log message:
graphics/py-plotly: Python graphing library

Plotly is an interactive, open-source, and browser-based graphing
library for Python.

Built on top of plotly.js, plotly.py is a high-level, declarative
charting library. plotly.js ships with over 30 chart types, including
scientific charts, 3D graphs, statistical charts, SVG maps, financial
charts, and more.