merge with 3.20.12

Added tag 3.20.12, debian/3.20.12-1, centos/3.20.12-1 for changeset 03e8fc9f79a6

[tox] Ensure pytest gets run with virtualenv's python

[tox] Use generating environments Drop the "env" option, which is unknown, and set a generative_ "envlist". Then use conditional dependencies based on factors_ to avoid repeating environment sections. The only singular one is the "cubicweb" environment because of its "commands". At some point, it'd be nice to find a way to have python version prefixes (py27-hooks or py34-web) for environment names but I could not find a way to extract the package name from such names. .. _generative: http://tox.readthedocs.org/en/latest/config.html#generative-envlist .. _factors: http://tox.readthedocs.org/en/latest/config.html#factors-and-factor-conditional-settings

a bit of pep8

[adapters] Use an adapter for serializing entities to a bare python structure which may be used for e.g. JSON export or other and allow to have different serializations for each entity types. Closes #6378035

[pkg] 3.20.12

[dataimport] Fallback from COPY to executemany (closes #9135780) If we can't build a suitable COPY command (e.g. because data has unsupported type), use executemany instead. Regression introduced in 3.20.0.

[web/views] unlink svg temp file after we're done Otherwise we fill up the tempdir. Closes #9133268.

Use cubicweb._