Support file output from FITS diff given path name
Fix the reporting of errors in files where TEST_UNICODE_LITERALS is
enabled.
Merge pull request #2987 from mdboom/test/fix-unicode-literals-error-reporting

Tests with TEST_UNICODE_LITERALS don't report errors correctly
Address embray comments, fix UnboundLocalError
Update test_diff.py

Remove extraneous whitespace
Explicitly specify axis for take in order to support multidimensional arrays
Added regression test
Added changelog entry
Added a new function to convert SkyCoord to pixel coordinates
Added missing imports
Add origin parameter
Added pixel_to_skycoord and unit test
Fix instantiation of SkyCoord
Implement mode option to select between full transformation (including distortions) and pure WCS. Extend tests.
Added changelog entry
Made has_distortion a property
Minor rewording
Updated changelog
fix bug in z_at_value
add test checking fix