Getting "*** failed to import extension" errors after upgrading to 1.5.1

[Pavel Shevaev]

Folks, I have upgraded my mercurial installation to 1.5.1 version and
now hg can't find extensions.

I used to have mercurial installed by apt-get, first I removed it by
running "apt-get --purge remove mercurial" and then installed
mercurial from the source manually.

Looks like it can't find the directory with built-in extensions for
some reason. it's strange because it's definitely in PYTHONPATH: I
added "print sys.path" into /usr/local/bin/hg and now when running hg
it shows something like this:

['/usr/local/bin', ... '/usr/local/lib/python2.6/dist-packages']

... and /usr/local/lib/python2.6/dist-packages/hgext does contain the
required extension(fetch in my case)

What am I doing wrong?

-- Best regards, Pavel