In certain situations (python23.dll and python23.zip in
the same dir, no PYTHON related env vars set, no Python
registry values), Python will fail to import site.

Exception is:
import site # loaded from Zip
C:\build\mozilla\dist\bin\python23.zip\site.pyo
'import site' failed; traceback:
Traceback (most recent call last):
  File ".\site.py", line 191, in ?
NameError: name 'sitedir' is not defined

This exception is the result of there being no
"prefixes", so sitedir is never bound to a value. 
This, the del of sitedir fails.

Suggested patch is attached (just setting sitedir to
None before the loop)

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"sitedir = []" would be a better choice.

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The exception is "sitedir" - but I do concede a better patch
would involve sitedirs=[]; sitedir=None and zapping both. 
However, as site is executed as a standard module, the
cleanup of the namespace seems a little anal - especially
now we have __all__ - so maybe deleting the dels would be
better still <wink>

But given we are so close to release, and that the 'noun' in
the exception is singular, I still prefer None (but I would
be happy to settle for sitedir="winK" #wink)

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Then None it is.

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Looks good to me, OK to check in AFAIC.

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Closing, as Jeremy said he applied this for 2.3c1.