Expose service errors to users

[y4izus]

Summary

Fix #2

Details and comments

To check the code, we first checked the swagger to see the service errors coming from the transpile endpoint. Then we run the ai-transpiler-demo jupyter notebook to test through the client and check if we get the same error messages.

We did some checks to make sure error messages are exposed:

• Try to access a backend we don't have access to
• Try to access a backend that doesn't exist
• Try to run a circuit with more gates than allowed
• An input with wrong format
• I was asked to try to run a task by an unexisting id, but it looks like this check makes no sense on the client
• Try to run a task that is failing. We had this code that was failing, but we checked it and it works, so we don't know how to try this check. If any of you have an idea, please let me know Thank you @jesus-talavera-ibm for your help here

Tests have been created to check the error messages

Thank you @victor-villar for helping me building the code to check the different situations

[jesus-talavera-ibm]

LGTM!

[victor-villar]

Thanks!