[Client] Improve HTTP error log

[animeshk08]

Current if an HTTP error is thrown by an API the log print error.response.reason as a result of

grimoirelab-perceval/perceval/client.py

Line 181 in 7f4cceb

response.raise_for_status()

However, many times the actual reason for the error is returned in ``error.response.text`. A log message can be printed in case an exception is thrown. This will help users to easily debug the error and also possibly avoid the need of such checks:

grimoirelab-perceval/perceval/backends/core/groupsio.py

Line 214 in 7f4cceb

if not group_download_archive:

grimoirelab-perceval/perceval/backends/core/pagure.py

Line 314 in 7f4cceb

if error.response.status_code == 404 and str(error.response.reason).upper() == 'NOT FOUND':

[valeriocos]

Thank you @animeshk08 for opening this issue and providing the fix.