Special handling of bytes_repr for mock filesets

[tclose]

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Summary

Implements special bytes_repr function for mocked filesets in(i.e. produced by Nifti1.mock("/path/to/mock")) as the fileset one yields the file mtimes in the cache key, which obviously don't exist for mocked files.

Checklist

• I have added tests to cover my changes (if necessary)
• I have updated documentation (if necessary)

[codecov]

Codecov Report

Attention: Patch coverage is 69.23077% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 84.23%. Comparing base (7d84fba) to head (bdf6abf).
Report is 2 commits behind head on master.

❗ Current head bdf6abf differs from pull request most recent head dd6fa8a

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Files	Patch %	Lines
pydra/utils/hash.py	69.23%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #743       +/-   ##
===========================================
+ Coverage   15.14%   84.23%   +69.09%     
===========================================
  Files          53       26       -27     
  Lines       15693     5137    -10556     
  Branches     2788     1450     -1338     
===========================================
+ Hits         2376     4327     +1951     
+ Misses      12988      804    -12184     
+ Partials      329        6      -323     

Flag	Coverage Δ
unittests	84.23% <69.23%> (+69.12%)	⬆️

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[effigies]

I don't like putting test code in main modules. What about adding pydra.testing.fixtures and including:

@pytest.fixture(scope='session')
def register_mock_mixin_serializer():
    @register_serializer(MockMixin)
    ...

Then in conftest.py:

from pydra.testing.fixtures import register_mock_mixin_serializer

This would allow downstream tools that need this feature to also put this import in their conftest.py.

[tclose]

I agree with the sentiment in general, but in this case I reckon that might be creating a gotcha that would take a bit of tracking down how to solve for little practical benefit, i.e if someone creates a new task package and wants to write a doctest using NiftiGz.mock(), then they would need to know that they also have to add this fixture