Some framework tests require tomopy

[yousefmoazzam]

In work on trying to reduce the usage of conda packages in httomo installation (#564) it was discovered that there are four UI layer tests that are part of what is currently classified as "framework" tests, that require tomopy to be installed to be able to run:

test_pipeline_build_duplicate_id
test_pipeline_build_cpu_pipeline
test_build_pipeline_with_param_sweeps
test_build_pipeline_with_param_sweeps

It may be worth either:

• trying to remove the dependency on tomopy in framework tests
• or, rethink the classification of what is part of the framework and what isn't (ie, the UI layer is one of the outermost layers of httomo, it could therefore be argued that it's not part of the core framework, and thus it may be fine for the UI layer to depend on tomopy - but in this case, it may then make sense to exclude the UI layer tests from the "framework" tests)

[dkazanc]

Yes, it is probably make sense to move those tests to where the backends tested, i.e., outside the general framework in our understanding.