Broken metadata error propagation

[JoranAngevaare]

What is the problem / what does the code in this PR do

This is a very simple PR and a small test to go with it for good practice.

Broken metadata (e.g. due to killed jobs) can cause headaches. It's sometimes very unclear where the error comes from as a lot of metadata may be scanned for building the tree of plugins to be processed

Can you briefly describe how it works?

Add more info to the traceback

What is the advantage?

The context can now recognize that something is wrong with the data and can rebuild the data when asked

Test example.

Running the test one can see the difference in errors

Before

json.decoder.JSONDecodeError: Extra data: line 176 column 2 (char 5406)

After

strax.storage.common.DataCorrupted: Cannot open metadata in /tmp/strax_data/0-records-j3nd2fjbiq from Extra data: line 176 column 2 (char 5406)

[jmosbacher]

Looks like a very good idea and I like the implementation of moving the actual logic to an internal method and wrapping it with a try, except block in the public method.
Just one question, why not do this in the base class and have all subclasses implement the private method instead of the public one?

[JoranAngevaare]

Looks like a very good idea and I like the implementation of moving the actual logic to an internal method and wrapping it with a try, except block in the public method. Just one question, why not do this in the base class and have all subclasses implement the private method instead of the public one?

Nice idea Yossi, thanks, let me change it!

[jmosbacher]

Looks good to me.