Update report feature with new argument, add temp fix for ifcfg module

[claireyywang]

Import error added in network.py as a temporary fix for ifcfg module. Will remove and update with build dependency once a deb package is ready.

This is an enhancement to report feature based on previous discussion #319 (comment)

This PR adds --report_failed argument, which allows user to only print report of failed checks. Major changes happen in format.py and doctor.py files.

Report content is output from each check module and indexed by their module names in generate_report(). They are printed out by calling format_print(modules, report). The function takes module names and print out their indexed report, with dynamically allocated space padding computed by compute_padding.

[claireyywang]

Linux
Linux-aarch64
OSX
Windows

[sloretz]

looks great! A few comments/nitpicks below

[claireyywang]

Linux
Linux-aarch64
OSX
Windows

[claireyywang]

Linux

[claireyywang]

Linux

[sloretz]

quick review

[sloretz]

The current try/except ValueError block doesn't guard against buggy reports and checks. Also, the second () is calling __init__(self) on the user's class, so it could raise too.

try:
    report_class = report_entry_pt.load()()
    report_category = report_class.category()
    report = report_class.report()
except Exception:
    # Checking `Exception` because buggy code could raise anything
    # Maybe traceback.format_exc() would be something to output here too?
    doctor_warn('Report class from %s failed to run.' % report_entry_pt.name)

[claireyywang]

linux
linux-aarch64
osx
windows

[claireyywang]

Linux
Linux-aarch64
OSX
Windows