cubicweb #14680828 handle recommends (e.g. psycopg2) in python packaging [waiting feedback]

traceback on cubicweb-ctl create when postgresql dependency missing

Run db-create to create the system database ? [Y/n]:
Traceback (most recent call last):
File "/home/arthur/.virtualenvs/fevis/bin/cubicweb-ctl", line 4, in <module>
  run(sys.argv[1:])
File "/home/arthur/.virtualenvs/fevis/local/lib/python2.7/site-packages/cubicweb/cwctl.py", line 1140, in run
  CWCTL.run(args)
File "/home/arthur/.virtualenvs/fevis/local/lib/python2.7/site-packages/logilab/common/clcommands.py", line 136, in run
  sys.exit(command.main_run(args, rcfile))
File "/home/arthur/.virtualenvs/fevis/local/lib/python2.7/site-packages/logilab/common/clcommands.py", line 265, in main_run
  self.run(args)
File "/home/arthur/.virtualenvs/fevis/local/lib/python2.7/site-packages/cubicweb/cwctl.py", line 434, in run
  helper.postcreate(self.config.automatic, self.config.config_level)
File "/home/arthur/.virtualenvs/fevis/local/lib/python2.7/site-packages/cubicweb/server/serverctl.py", line 204, in postcreate
  self.config.appid])
File "/home/arthur/.virtualenvs/fevis/local/lib/python2.7/site-packages/logilab/common/clcommands.py", line 136, in run
  sys.exit(command.main_run(args, rcfile))
File "/home/arthur/.virtualenvs/fevis/local/lib/python2.7/site-packages/logilab/common/clcommands.py", line 265, in main_run
  self.run(args)
File "/home/arthur/.virtualenvs/fevis/local/lib/python2.7/site-packages/cubicweb/server/serverctl.py", line 386, in run
  helper = get_db_helper(driver)
File "/home/arthur/.virtualenvs/fevis/local/lib/python2.7/site-packages/logilab/database/__init__.py", line 72, in get_db_helper
  return _ADV_FUNC_HELPER_DIRECTORY[driver]()
File "/home/arthur/.virtualenvs/fevis/local/lib/python2.7/site-packages/logilab/database/__init__.py", line 765, in __init__
  self.dbapi_module = get_dbapi_compliant_module(self.backend_name)
File "/home/arthur/.virtualenvs/fevis/local/lib/python2.7/site-packages/logilab/database/__init__.py", line 79, in get_dbapi_compliant_module
  mod = _ADAPTER_DIRECTORY.adapt(driver, prefered_drivers, pywrap=pywrap)
File "/home/arthur/.virtualenvs/fevis/local/lib/python2.7/site-packages/logilab/database/__init__.py", line 195, in adapt
  module, modname = _import_driver_module(driver, prefered_drivers)
File "/home/arthur/.virtualenvs/fevis/local/lib/python2.7/site-packages/logilab/database/__init__.py", line 232, in _import_driver_module
  raise ImportError('Unable to import a %s module' % driver)
ImportError: Unable to import a postgres module
priorityminor
typeenhancement
done in<not specified>
closed by<not specified>