util: use zc.buildout.download API to download schema

This will support buildout extension to download from gitlab API with
authentication.

The code has already been refactored a bit to be able to pass a
download instance to SoftwareReleaseSchema, for now to instanciate only
one Download but in the future this might be extended to pass some
configuration to the Download instance.
9 jobs for feat/schema-buildout in 0 seconds
Status Job ID Name Coverage
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passed SlapOS.Eggs.UnitTest-TestRunner1.Python3

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passed SlapOS.Eggs.UnitTest-TestRunner1.Python2

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passed SlapOS.Eggs.UnitTest-TestRunner1.Python2

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passed SlapOS.Eggs.UnitTest-TestRunner1.Python2

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failed SlapOS.Eggs.UnitTest-TestRunner1.Python3

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failed SlapOS.Eggs.UnitTest-TestRunner1.Python3

failed SlapOS.Eggs.UnitTest-TestRunner1.Python3

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passed SlapOS.Eggs.UnitTest-TestRunner1.Python3

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