Raise DestinationExistsError from EEXIST.

[bdice]

Description

This should fix some intermittent failures seen on CI. It may need to be run on CI a few times to ensure that this fixes the problem.

See issue #431 for a full description of the issue this aims to resolve.

Motivation and Context

Fix CI failures relating to POSIX error code handling.

Types of Changes

• Documentation update
• Bug fix
• New feature
• Breaking change¹

¹The change breaks (or has the potential to break) existing functionality.

Checklist:

• I am familiar with the Contributing Guidelines.
• I agree with the terms of the Contributor Agreement.
• My name is on the list of contributors.
• My code follows the code style guideline of this project.
• The changes introduced by this pull request are covered by existing or newly introduced tests.

If necessary:

• I have updated the API documentation as part of the package doc-strings.
• I have created a separate pull request to update the framework documentation on signac-docs and linked it here.
• I have updated the changelog and added all related issue and pull request numbers for future reference (if applicable). See example below.

[codecov]

Codecov Report

Merging #433 (4e8681e) into master (648760d) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #433   +/-   ##
=======================================
  Coverage   76.59%   76.59%           
=======================================
  Files          45       45           
  Lines        7079     7079           
=======================================
  Hits         5422     5422           
  Misses       1657     1657           

Impacted Files	Coverage Δ
signac/contrib/import_export.py	85.44% <100.00%> (ø)
signac/contrib/job.py	92.80% <100.00%> (ø)

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[atravitz]

This looks good, we should merge before #429. Do we need to run CI a few more times first?

[klywang]

Looks good!

@atravitz I think it would be a good idea to run CI a few more times, just to be safe.

[bdice]

I'm happy with the level of success on this PR, it ran without any failures for at least 4 test commits. We would expect to see failures by this point if the problem hadn't been solved. I'm going to go ahead and merge this to prevent further CI failures on other PRs.