Broken tutorial: default configuration

[lasofivec]

With PR #327 the following lines were introduced

tofu/tofu/geom/utils.py

Lines 886 to 888 in 7a3aca1

	msg = get_available_config(verb=False, returnas=str)
	raise Exception(msg)
	# case = _DEFCONFIG

this breaks the tutorial for plotting the gallery of fusion machines. In particular the lines:

config = tf.geom.utils.create_config() # create default configuration

We can either:

• restore a default configuration creation
• change the tutorial and plot a specific configuration

[Didou09]

Good point,
I changed this to make sure that when the user does not specify a config, a new error message appears that shows all available configurations.
I think this is better since it automatically informs the user about all options he/she has.

Based on my experience that when a user meets a new function, first reflex is to to just use it without reading the docstr and see what happens.
In such a case, it should either:

• Option 1 : work out-of-the-box
  It was the case before the PR, it was automatically loading ITER. But it does not tell the user how to use the function if he/she wants to do something else
• Option 2: throw an error message that explains how to use it

We were in option 1 before the PR, we are now in option 2: the error message is explicit, shows the available config and how to load them.

Option 2 has my preference, but this is clearly a question of taste, we can go back to option 1 if you prefer, what do you think ?

[lasofivec]

If the tutorial is the only place where the function was being called as such, I agree that option 2 is more tasteful.

The tutorial can call:
config = tf.geom.utils.create_config("ITER")

[Didou09]

Good for me, can you update it ? :-)

[Didou09]

Fixed in devel by PR #333