Issue 139 raise more specific error for non existing asset

[rafalstepien]

• updated the dependencies
• cleaned up some parts of code
• added the test to reproduce error
• fixed the error by raising correct exception

[nsheff]

Hi @rafalstepien -- why do you need to force-push here?

[nsheff]

Also, did you figure out that pytest error?

[rafalstepien]

@nsheff I force pushed because I was squashing commits - I always do that before merging one branch to another.

As to the pytest error it has ben solved instantly when I changed the base of the branch from master to dev and rebased with dev.