Without this, one gets a UnicodeEncodeError if the intro contains non-ascii.

webbrowser should do the right thing on any platform.

Still does not pass tests, but goes a bit further.

This is needed on 1.11.chamilo.org, which allows only one simultaneous
connection. Without this, the first access leaves a connection open, and
we don't even have the session cookie to close it later.

Also, don't try to connect if we're only going to dump Yaml.

Also, don't try to connect if we're only going to dump Yaml.

This is needed on GrenobleINP instance since ... yesterday (2/10/2016) it seems.

This reverts 0bea36de, "unit test for convert desc and <math>". Not sure
how I ended up with the duplicate :-(.

We don't want to start uploading if one of the quiz contain a syntax
error. Open (and therefore) check all of them before opening the
connection.

Fixes #13.

Also, reuse the same connection for all quiz files. This is not only to
save a few network round-trips, but also to avoid typing the password
several times.

Unfortunately, we need a hack to keep it working in Python 2.

We already allow

  chamilotools -u foo -u bar

with last-one-wins semantics. Allow

  chamilotools -u foo COMMAND -u bar

with the same. A nice side effect is that it unifies the boolean and the
string merging code.

This is a workaround for what seems to be a bug in argparse (fixed in
Python 3.4).