CoverageException: Can't add arcs to existing line data

[nedbat]

Originally reported by Anonymous

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While testing with:
coverage==4.0.3
django-nose==1.4.3

With arguments:
'--cover-branches',
'--with-coverage',
'--cover-package=personalfinance.services',

I get:

File "pythonenv\lib\site-packages\coverage\data.py", line 363, in add_arcs
raise CoverageException("Can't add arcs to existing line data")
coverage.misc.CoverageException: Can't add arcs to existing line data

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• Bitbucket: https://bitbucket.org/ned/coveragepy/issue/476

[nedbat]

Please be sure to clean existing data files before running coverage. Can you provide instructions on reproducing the problem?

[nedbat]

If you can provide more details, feel free to re-open this issue.

[nedbat]

Original comment by bouteillebleu (Bitbucket: bouteillebleu, GitHub: bouteillebleu)

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Not the original raiser of the issue, but finding this was useful - I ran into the same error (having first done a run without --cover-branches), but putting --cover-erase into the command line as well made it run correctly. Thank you Ned for the note about cleaning existing data files before running coverage again.