Dependency missing

[observingClouds]

When opening a file with preffs after a fresh install, not all packages are installed:

A suitable version of pyarrow or fastparquet is required for parquet support.
Trying to import the above resulted in these errors:
 - Missing optional dependency 'pyarrow'. pyarrow is required for parquet support. Use pip or conda to install pyarrow.
 - Missing optional dependency 'fastparquet'. fastparquet is required for parquet support. Use pip or conda to install fastparquet.

Although the message is very clear on what to do, preffs should probably check if either of these packages are installed and otherwise install one by default.

[d70-t]

Sounds reasonable, but I don't know a method how to do it...
The options I konw of would be:

• choose one of the two as a direct dependency, but that would be overly restrictive
• or we could make both an optional dependency, but in that case neither would be installed by default...

I think the freedom to choose as given by pandas meens that ultimately it should be up to the the user (or maybe a creator of an executable style package) to decide which option to use. So someone will have to put a direct dependency, but maybe that should be further downstrem in the stack...