Challenge submission error handling

If the challenge ID or phase does not exist on EvalAI server, the CLI should respond with necessary error, but the CLI crashes with the error as shown below -

Image Courtesy: GCI Student aaaakshat

Reproduce a challenge submission using a nonexistent challenge ID or phase and inspect where the CLI crashes. Trace the submission command from the resulting error, then make the CLI return a necessary user-facing error instead of crashing. Done when both invalid-input cases are handled consistently.

Written by the indexing model from the issue text.