to keep tests silent.

On python2, this uses subprocess32, which backports DEVNULL (and
default setting of closing file descriptors).

subprocess32 backports the good things from python3's subprocess and is
recommended on https://docs.python.org/2/library/subprocess.html

it's now configured in tests/__init__.py

When running tests we don't want to clutter the output with logs.
Environment variable SLAPOS_TEST_DEBUG can be set to restore the
verbosity

Instead of printing when passed log=True, always log at DEBUG level,
application can decide what to do with these logs.

This will let the connection parameters with multilines value be correctly displayed.

I also fixed the linter.

/reviewed-on !74

slapos_crm: testSlapOSCRMSkins: The order of the elements of portal_catalog are not always the same.

Probably incomplete as we need to check for activities.

/reviewed-on nexedi/slapos.core!71

/reviewed-on nexedi/slapos.core!70

[slapos_crm] fix failing crm skins tests after include error message in generated ticket for hosting subscription

After c931d60c, default options were changed and we didn't want that.

Rewrite the code so that we have a clearer scheme:
 * all options of format are listed as FormatConfig attributes with default values
 * all values present in configuration file (.cfg) erase the previous options
 * all values present in command line erase the previous options

We use the special default argparse.SUPPRESS that removes totally the arg from arg dict so that only PRESENT options erase something

fix after nexedi/slapos.core!62

@rafael currently slapos node boot is broken on all machines with ipv6_interface different from interface_name (e.g. rapid space machines)

/reviewed-on nexedi/slapos.core!68

ComputerModelModule_viewComputerModelList was commited by mistake

Some informations are important to have.