make py lib a self-contained directory again

- move and merge _py/ bits back to py/
- fixes all around

--HG--
branch : trunk

py/impl/code/oldmagic.py

@@ -0,0 +1,62 @@
+""" deprecated module for turning on/off some features. """ 
+
+import py 
+
+from py.builtin import builtins as cpy_builtin
+
+def invoke(assertion=False, compile=False):
+    """ (deprecated) invoke magic, currently you can specify:
+
+        assertion  patches the builtin AssertionError to try to give
+                   more meaningful AssertionErrors, which by means
+                   of deploying a mini-interpreter constructs
+                   a useful error message.
+    """
+    py.log._apiwarn("1.1", 
+        "py.magic.invoke() is deprecated, use py.code.patch_builtins()",
+        stacklevel=2, 
+    )
+    py.code.patch_builtins(assertion=assertion, compile=compile)
+
+def revoke(assertion=False, compile=False):
+    """ (deprecated) revoke previously invoked magic (see invoke())."""
+    py.log._apiwarn("1.1", 
+        "py.magic.revoke() is deprecated, use py.code.unpatch_builtins()",
+        stacklevel=2, 
+    )
+    py.code.unpatch_builtins(assertion=assertion, compile=compile)
+
+patched = {}
+
+def patch(namespace, name, value):
+    """ (deprecated) rebind the 'name' on the 'namespace'  to the 'value',
+        possibly and remember the original value. Multiple
+        invocations to the same namespace/name pair will
+        remember a list of old values.
+    """
+    py.log._apiwarn("1.1", 
+        "py.magic.patch() is deprecated, in tests use monkeypatch funcarg.", 
+        stacklevel=2, 
+    )
+    nref = (namespace, name)
+    orig = getattr(namespace, name)
+    patched.setdefault(nref, []).append(orig)
+    setattr(namespace, name, value)
+    return orig
+
+def revert(namespace, name):
+    """ (deprecated) revert to the orginal value the last patch modified.
+        Raise ValueError if no such original value exists.
+    """
+    py.log._apiwarn("1.1", 
+        "py.magic.revert() is deprecated, in tests use monkeypatch funcarg.",
+        stacklevel=2, 
+    )
+    nref = (namespace, name)
+    if nref not in patched or not patched[nref]:
+        raise ValueError("No original value stored for %s.%s" % nref)
+    current = getattr(namespace, name)
+    orig = patched[nref].pop()
+    setattr(namespace, name, orig)
+    return current
+