copy immutabledict here to remove dependency on sqla 0.7, [#36]

alembic/ddl/impl.py

@@ -5,7 +5,6 @@
 from alembic.ddl import base
 from alembic import util
 from sqlalchemy import types as sqltypes
-from sqlalchemy import util as sqla_util
 
 class ImplMeta(type):
     def __init__(cls, classname, bases, dict_):
@@ -58,7 +57,7 @@ def bind(self):
 
     def _exec(self, construct, execution_options=None, 
                             multiparams=(), 
-                            params=sqla_util.immutabledict()):
+                            params=util.immutabledict()):
         if isinstance(construct, basestring):
             construct = text(construct)
         if self.as_sql:

alembic/util.py

@@ -210,3 +210,34 @@ def __get__(self, obj, cls):
         obj.__dict__[self.__name__] = result = self.fget(obj)
         return result
 
+
+class immutabledict(dict):
+
+    def _immutable(self, *arg, **kw):
+        raise TypeError("%s object is immutable" % self.__class__.__name__)
+
+    __delitem__ = __setitem__ = __setattr__ = \
+    clear = pop = popitem = setdefault = \
+        update = _immutable
+
+    def __new__(cls, *args):
+        new = dict.__new__(cls)
+        dict.__init__(new, *args)
+        return new
+
+    def __init__(self, *args):
+        pass
+
+    def __reduce__(self):
+        return immutabledict, (dict(self), )
+
+    def union(self, d):
+        if not self:
+            return immutabledict(d)
+        else:
+            d2 = immutabledict(self)
+            dict.update(d2, d)
+            return d2
+
+    def __repr__(self):
+        return "immutabledict(%s)" % dict.__repr__(self)