Feedback from processing algorithms may be mistaken for plugin issue

#### Here's what I did
1. I issued an invalid request from the _Directions from 1 Point Layer_ processing algorithm:
My input layer had duplicate points, which traveling salesman optimization doesn't allow, but I turned on traveling salesman.

2. I issued a request from the same algorithm to the public API, but without configuring a key first.
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#### Here's what I got
As expected, the log contained information about the issue in both cases:
1. 
2. 

In both cases, this output seemed as if there was an issue with the plugin.
In both cases, the issue was not with the plugin, but with my input - one time it was faulty, one time I had no key configured.

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#### Here's what I think could be improved
How can we give feedback from the processing plugins in a way that tells the user that something is wrong that they can fix themselves, rather than it being an issue with the plugin?