Improve error catching and message for add

[chStaiger]

Improve error message as decsribed in #289

[qubixes]

Thanks! I do think the old way had some advantages that we lose in the new implementation. Namely, if PRC / server implements these and there is no more error, the code will immediately work on our side as well. Perhaps the best would be to catch the TypeError, and reraise it with the new text if key/value is None, else reraise the original error.

[qubixes]

I think technically, key is None should raise a TypeError and key == "" should raise a ValueError. Perhaps it makes the most sense to raise a TypeError in this case? We could also split it, but that may be too much for this technical detail.

[chStaiger]

TO be pragmatic, I will turn them into TypeErrors.

[chStaiger]

I tried to trigger the except irods.message.Bad_AVU_Field, but it crashes beforehand in e.g. our blacklist check with regular expressions. So we de facto we are not making any use of this error.
Here a list:

• if the key is None the regex fails
• if the key is '' we get this error from the PRC: ValueError: Empty value in <iRODSMeta None bla None>
• The PRC does not catch the error if the value is None: TypeError: object of type 'NoneType' has no len()
• And if the value is '' we get the same error as above ValueError: Empty value in <iRODSMeta None Bla None>. So from those errors it is not clear whether the key causes the problem or the value

[qubixes]

I tried to trigger the except irods.message.Bad_AVU_Field, but it crashes beforehand in e.g. our blacklist check with regular expressions. So we de facto we are not making any use of this error. Here a list:

* if the key is None the regex fails

* if the key is `''` we get this error from the PRC: `ValueError: Empty value in <iRODSMeta None  bla None>`

* The PRC does not catch the error if the value is None: `TypeError: object of type 'NoneType' has no len()`

* And if the value is `''` we get the same error as above `ValueError: Empty value in <iRODSMeta None Bla  None>`. So from those errors it is not clear whether the key causes the problem or the value

I'm quite sure I have seen the error at some point. What about other types? Like key/value being an integer? Does the blacklist check error you get when key == None make sense?

[chStaiger]

When I use a list or a tuple, then I hit the irods exception TypeError: Value should have type str or bytes-like, not <class 'list'>.. For integers I get the TypeError: object of type 'int' has no len()

[chStaiger]

The error from the re.match function when provided None is a bit meager:
TypeError: expected string or bytes-like object, got 'NoneType'

The user does not really know what went wrong and which part of the metadata item is the culprit.

[chStaiger]

I think I got it now right. In the "add" function there is an extra TypeError that catches the failure of the comparison between ley and blacklist. I added again the BadAVU exception and only replaced its message when something is wrong with the key to stay consitstent that in iBridges we call attributes keys.

@qubixes Can you please review again.

[qubixes]

Still some questions, but we're almost there!

[qubixes]

I think it should be in the old place. Now, we don't know whether the new one was already added.

[qubixes]

Which error are we ignoring here? Can't we add an annotation?

[qubixes]

Same here.