At the present time (Py2.4):
"""
Under Unix, if the environment variable BROWSER exists,
it is 
interpreted to override the platform default list of
browsers,...
"""
(extract from
Python-2.4/Doc/html/lib/module-webbrowser.html)

But, when the environment variable BROWSER is messed up,
there is no reason not to try the other detected
browser alternatives.

In this patch, if the BROWSER variable is Ok, than it
is respected.
Otherwise, the previously detected browsers are tryied
out as if
BROWSER variable never existed.

This does not break backward compatibility and adds
more chance
for webbrowser.open() to succeed.

This patch was made against CVS head 2005-03-20, and
aims to 2.5, but can safely be apllied to any 2.4.x bug
fix release.