Log level for data read is too low

[spassmoor]

When reading data that is not found in the archive the log level is set to debug and the missing data is filled in with zeros. This should be a warning level output
example
DEBUG: Starting new HTTPS connection (1): archive-gw-1.kat.ac.za:443
DEBUG: https://archive-gw-1.kat.ac.za:443 "GET /1537611365_sdp_l0/correlator_data/00004_01920_00000.npy HTTP/1.1" 404 230

[ludwigschwardt]

First off, it's better to make SPR1 JIRA tickets if you are within SARAO to avoid falling off the radar :-D

Now, on missing data, there are three cases I am interested in:

• The data was never in the archive. This happens at the start and end of nearly all observations and should not turn into a warning.
• The data is in the archive but we struggled to retrieve it. This could become a warning, but I'm not keen on a sea of logs.
• No data is in the archive, because the dataset has moved to tape. This needs an entirely different error message (SPR1-766).

There is a ticket (SPR1-891) to collect all the statistics of archive errors and present that at the end. Or do you want some kind of running commentary?