Diagnostic mode is intended to be used for rebar3 maintainers to debug
and understand issues. It shows all the things and all the data and
works with the assumption that people has intent to use the source code
to debug things.

Debug mode is promoted to user-oriented debugging, based on the idea
that what they care about is figuring out their interactions with the
tool. A major improvement in usability would be to directly tie the user
config to the interpreted config (ie merged profiles) to clearly hint at
seen rebar3’s behaviour.  If the debug output can show that and even tie
some behaviours to the config value that impacts things, we could get
some discoverability out of it too, something missing from declarative
tools like this.

In some cases, such as when the global rebar.config file contains typoes
and invalid terms, the rebar3 executable fails when trying to log the
error since it hasn't been set yet, such as in #1792

This patch fixes that by going for a fallback mechanism.

This is done through 3 main change groups:

- replacing `~s` by `~ts` in format strings, so that strings that
  contain unicode are properly printed rather than crashing
- adding the `unicode` argument to all function of the `re` module to
  ensure transformations on strings containing unicode data are valid
  instead of crashing (see issue #1302)
- replacing `ec_cnv:to_binary/1` and `ec_cnv:to_list/1` with matching
  functions in `rebar_utils`.

The last point has been done, rather than modifying and updating erlware
commons, because binary and list conversions can be a contentious
subject. For example, if what is being handled is actually bytes from a
given binary stream, then forcing a byte-oriented interpretation of the
data can corrupt it. As such, it does not appear safe to modify erlware
commons' conversion functions since it may not be safe for all its
users.

Instead, rebar3 reimplements a subset of them (only converting
atoms and chardata, ignoring numbers) with the explicit purpose of
handling unicode string data.

Tests were left as unchanged as possible. This may impact the ability to
run rebar3's own suites in a unicode path, but respects a principle of
least change for such a large patch.

--HG--
extra : rebase_source : 60b49fa683