Some minor changes from error handling refactor #74

[joelvdavies]

Description

Applies some minor changes found while working on #517.

• The TestDelete in e2e/test_item.py showed different error messages getting an item and deleting one that doesn't exist when they could be the same
• test_update_name_to_duplicate in TestUpdate inside test_manufacturer.py (repositories) - did not actually call or assert anything

Testing instructions

Add a set up instructions describing how the reviewer should test the code

• Review code
• Check Actions build
• Review changes to test coverage

Agile board tracking

Relates to #74

The base branch was changed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.36%. Comparing base (94f0015) to head (2c87835).
Report is 4 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #562      +/-   ##
===========================================
+ Coverage    89.11%   89.36%   +0.25%     
===========================================
  Files           51       51              
  Lines         1865     1900      +35     
===========================================
+ Hits          1662     1698      +36     
+ Misses         203      202       -1     

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