zope.app.component broken with zope.component 3.8.0 and greater?

Hello,

I'm trying to update my application to use the recent patch that Tres
Seaver helpfully landed on zope.app.testing.

The new zope.app.testing seems to require a new zope.component, since
it's importing hooks from z.component rather than zope.site.

However, when I update zope.component, I get the following error from
zope.app.component:

Traceback (most recent call last):
...
  File ".../zope.app.component-3.8.3-py2.5.egg/zope/app/component/metaconfigure.py",
line 15, in <module>
    from zope.component.zcml import PublicPermission, _checker, view, resource
ImportError: cannot import name PublicPermission

It appears that r83 of lp:zope.component moves PublicPermission from
zope.component.zcml to zope.component.security.

Now, my app is only using metaconfigure in this instance to get at
PublicPermission and view, so I might as well import them from
zope.component directly, solving my immediate problem.

However, this still leaves zope.app.component broken with new
zope.component releases.

I can't find the code for zope.app.component on Launchpad, but the fix
seems pretty simple – import PublicPermission from
z.component.security.

It seems to me that zope.component is also broken, since moving
PublicPermission to a new module breaks backwards compatibility. I've
attached a patch that goes some way to fixing this.

More generally, I'm a bit worried that this attempt of mine to upgrade
the zope.testing that my app uses is going to result in a cascade of
dependency upgrades, each with their own little backwards
compatibility problems. What sort of expectations should I have? e.g.
Do the version numbers tell me anything about intended compatibility?

Thanks,
jml

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=== modified file 'src/zope/component/zcml.py'
--- src/zope/component/zcml.py	2010-04-06 03:01:29 +0000
+++ src/zope/component/zcml.py	2010-04-11 14:24:49 +0000
@@ -30,7 +30,7 @@
 try:
     from zope.component.security import _checker, proxify, protectedFactory, \
         securityAdapterFactory
-    from zope.security.zcml import Permission
+    from zope.security.zcml import Permission, PublicPermission
 except ImportError:
     SECURITY_SUPPORT = False
     from zope.schema import TextLine as Permission