Addressing USDOT comments regarding ISS Health Check & Firmware Manager

[dmccoystephenson]

Problem

Dan left a number of comments on usdot-jpo-ode#15 that need to be addressed.

Solution

The following changes have been made to address Dan's comments:

• Single-line comments have been replaced with docstrings in download_blob.py
• The upgrader.py file has been updated to raise an exception if an unsupported blob storage type is specified.
• A module-specific logger is now being used for the ISS Health Check addon.
• File type validation checks have been added to download_blob.py
• SCMS data validation checks have been added to iss_health_checker.py
• A comment was added in iss_health_checker.py to explain why the last character in the query is getting ignored.
• A wrapper class for rsu_data has been created in iss_health_checker.py to improve clarity regarding what attributes we expect to be setting in the dictionary.

Testing

• Unit tests pass with these changes
• Firmware Manager addon started up successfully on WYDOT's Test VM
• ISS Health Check addon started up successfully on WYDOT's Test VM
• ISS Health Check addon was able to process SCMS data successfully on WYDOT's Test VM

[payneBrandon]

lgtm!