[FIX] only download group maps when creating dataset and raise error if no images are found for a contrast

[jdkent]

Closes #579
ref #576

Changes proposed in this pull request:

• check if map is group-level
  • skip map if it is not group level
• check if any maps are found for a contrast
  • raise error if no images are found
• add test

[jdkent]

I do not have strong feelings about this being a warning instead, but I chose to raise an error since it could lead to errors down the line if you were trying to run a meta-analysis for a contrast with no images.

[tsalo]

I think an error is reasonable. If we see users complain about it a lot, we can revisit, but I agree that downgrading to a warning sounds problematic.

[tsalo]

There seems to be a new problem with isort. It also came up in ME-ICA/tedana#815. I haven't looked into it yet, but it might be a matter of pinning the version of flake8-isort. The build_docs error is random and already documented in #418.

I will try to look at the actual code soon.

[tsalo]

@jdkent it looks like the isort issue is fixed, although the current cache will have the bad version. If you update info.py or the CircleCI cache strings to trigger a new build, I think CI will pass.

[tsalo]

@jdkent all of the downstream jobs from the make_env_py36 job need to have the cache updated too. However, now that #578 is merged, I think you can just rebase and it should pass CI.

[codecov]

Codecov Report

Merging #580 (26c42cd) into main (05bbd89) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #580      +/-   ##
==========================================
+ Coverage   85.82%   85.83%   +0.01%     
==========================================
  Files          39       39              
  Lines        4267     4271       +4     
==========================================
+ Hits         3662     3666       +4     
  Misses        605      605              

Impacted Files	Coverage Δ
nimare/io.py	95.07% <100.00%> (+0.09%)	⬆️

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[tsalo]

LGTM!