magic-removal: Moved django/core/db/__init__.py to django/db/__init__.py and cleaned it up

git-svn-id: http://code.djangoproject.com/svn/django/branches/magic-removal@1635 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/__init__.py

@@ -0,0 +1,19 @@
+from django.conf.settings import DATABASE_ENGINE
+
+__all__ = ('backend', 'connection', 'DatabaseError')
+
+try:
+    backend = __import__('django.db.backends.%s.base' % DATABASE_ENGINE, '', '', [''])
+except ImportError, e:
+    # The database backend wasn't found. Display a helpful error message
+    # listing all possible database backends.
+    from django.core.exceptions import ImproperlyConfigured
+    import os
+    backend_dir = os.path.join(__path__[0], 'backends')
+    available_backends = [f[:-3] for f in os.listdir(backend_dir) if not f.startswith('_')]
+    available_backends.sort()
+    raise ImproperlyConfigured, "Could not load database backend: %s. Is your DATABASE_ENGINE setting (currently, %r) spelled correctly? Available options are: %s" % \
+        (e, DATABASE_ENGINE, ", ".join(map(repr, available_backends)))
+
+connection = backend.DatabaseWrapper()
+DatabaseError = dbmod.DatabaseError