[bugfix] Warn when a check search path does not exist

[ekouts]

Fixes #1928.

[vkarak]

I think the warning should be issued by the load_all() function of the loader:

https://github.com/eth-cscs/reframe/blob/23dc03bd2b85adcae62fb69be51a047e5cef1be5/reframe/frontend/loader.py#L205-L206

[teojgo]

I agree with @vkarak, this way you will also take into account the case where the checkpath is given by the env variable.

[ekouts]

I think the warning should be issued by the load_all() function of the loader:

https://github.com/eth-cscs/reframe/blob/23dc03bd2b85adcae62fb69be51a047e5cef1be5/reframe/frontend/loader.py#L205-L206

@vkarak @teojgo What about the case that the user doesn't pass any path? Should the warning appear when he passes nothing and there is no ${RFM_INSTALL_PREFIX}/checks/? That's why I made the check earlier.

[vkarak]

@ekouts I think the load_all() will cover that case, too. load_all() is always called to load the tests.

[ekouts]

Ok, then I will change it. I thought we don't want a warning in that case.

[vkarak]

We do want a warning there, too.

[codecov-commenter]

Codecov Report

Merging #1949 (e3ea0ae) into master (8b7f35e) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1949   +/-   ##
=======================================
  Coverage   87.91%   87.91%           
=======================================
  Files          50       50           
  Lines        8637     8638    +1     
=======================================
+ Hits         7593     7594    +1     
  Misses       1044     1044           

Impacted Files	Coverage Δ
reframe/frontend/loader.py	92.56% <100.00%> (+0.06%)	⬆️

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