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Sorry, I can't reproduce the problem. By default and by design, Library/Python/2.7/site-packages comes last in sys.path for the python.org installed Pythons. Are you sure you aren't overriding sys.path with a PYTHONPATH environment variable or some change to site.py?
$ /usr/bin/python2.7
Python 2.7.1 (r271:86832, Jun 16 2011, 16:59:05) 
[GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 23351500)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys; from pprint import pprint as pp ; pp(sys.path)
['',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python27.zip',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-darwin',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac/lib-scriptpackages',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-old',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload',
 '/Users/pyi/Library/Python/2.7/lib/python/site-packages',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/PyObjC',
 '/Library/Python/2.7/site-packages']
>>> import pysvn
>>> pysvn
<module 'pysvn' from '/Library/Python/2.7/site-packages/pysvn/__init__.py'>
>>> ^D
pyb7:~ pyi$ /usr/local/bin/python2.7
Python 2.7.2 (v2.7.2:8527427914a2, Jun 11 2011, 15:22:34) 
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys; from pprint import pprint as pp ; pp(sys.path)
['',
 '/Library/Frameworks/Python.framework/Versions/2.7/lib/python27.zip',
 '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7',
 '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-darwin',
 '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac',
 '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac/lib-scriptpackages',
 '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk',
 '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-old',
 '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload',
 '/Users/pyi/Library/Python/2.7/lib/python/site-packages',
 '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages',
 '/Library/Python/2.7/site-packages']
>>> import pysvn
>>> pysvn
<module 'pysvn' from '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pysvn/__init__.py'>
>>>