Add Alembic support from alchemy cookiecutter

[stevepiercy]

WIP. Should be backported to 1.9-branch only upon completion.

See #1597 and Pylons/pyramid-cookiecutter-alchemy#7

[stevepiercy]

@mmerickel I took a stab at merging the cookiecutter's default script with the tutorial's script from the models step. When I run it, I get an import error. See stack trace below.

I'm not sure whether the script is correct and I should wait until I fix the views in the next step to get it to run, or the script is wrong. Will pyramid.bootstrap only work when the app is in a runnable state?

$ env/bin/initialize_tutorial_db development.ini
Traceback (most recent call last):
  File "env/bin/initialize_tutorial_db", line 11, in <module>
    load_entry_point('tutorial', 'console_scripts', 'initialize_tutorial_db')()
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/tutorial/scripts/initialize_db.py", line 40, in main
    env = bootstrap(config_uri)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/pyramid/paster.py", line 107, in bootstrap
    app = get_app(config_uri, options=options)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/pyramid/paster.py", line 28, in get_app
    return loader.get_wsgi_app(name, options)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/plaster_pastedeploy/__init__.py", line 131, in get_wsgi_app
    global_conf=defaults)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/paste/deploy/loadwsgi.py", line 247, in loadapp
    return loadobj(APP, uri, name=name, **kw)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/paste/deploy/loadwsgi.py", line 272, in loadobj
    return context.create()
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/paste/deploy/loadwsgi.py", line 710, in create
    return self.object_type.invoke(self)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/paste/deploy/loadwsgi.py", line 146, in invoke
    return fix_call(context.object, context.global_conf, **context.local_conf)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/paste/deploy/util.py", line 55, in fix_call
    val = callable(*args, **kw)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/tutorial/__init__.py", line 11, in main
    config.scan()
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/pyramid/config/__init__.py", line 1043, in scan
    ignore=ignore)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/venusian/__init__.py", line 230, in scan
    __import__(modname)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/tutorial/views/default.py", line 6, in <module>
    from ..models import MyModel
ImportError: cannot import name 'MyModel'

[stevepiercy]

@mmerickel I took a stab at merging the cookiecutter's default script with the tutorial's script from the models step. When I run it, I get an import error. See stack trace below.

I'm not sure whether the script is correct and I should wait until I fix the views in the next step to get it to run, or the script is wrong. Will pyramid.bootstrap only work when the app is in a runnable state?

$ env/bin/initialize_tutorial_db development.ini
Traceback (most recent call last):
  File "env/bin/initialize_tutorial_db", line 11, in <module>
    load_entry_point('tutorial', 'console_scripts', 'initialize_tutorial_db')()
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/tutorial/scripts/initialize_db.py", line 40, in main
    env = bootstrap(config_uri)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/pyramid/paster.py", line 107, in bootstrap
    app = get_app(config_uri, options=options)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/pyramid/paster.py", line 28, in get_app
    return loader.get_wsgi_app(name, options)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/plaster_pastedeploy/__init__.py", line 131, in get_wsgi_app
    global_conf=defaults)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/paste/deploy/loadwsgi.py", line 247, in loadapp
    return loadobj(APP, uri, name=name, **kw)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/paste/deploy/loadwsgi.py", line 272, in loadobj
    return context.create()
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/paste/deploy/loadwsgi.py", line 710, in create
    return self.object_type.invoke(self)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/paste/deploy/loadwsgi.py", line 146, in invoke
    return fix_call(context.object, context.global_conf, **context.local_conf)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/paste/deploy/util.py", line 55, in fix_call
    val = callable(*args, **kw)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/tutorial/__init__.py", line 11, in main
    config.scan()
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/pyramid/config/__init__.py", line 1043, in scan
    ignore=ignore)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/env/lib/python3.5/site-packages/venusian/__init__.py", line 230, in scan
    __import__(modname)
  File "/Users/stevepiercy/projects/hack-on-pyramid/tutorial/tutorial/views/default.py", line 6, in <module>
    from ..models import MyModel
ImportError: cannot import name 'MyModel'

[stevepiercy]

@mmerickel ready for final review.

[stevepiercy]

@mmerickel ready for final review.

[mmerickel]

This looks great @stevepiercy.