The automatic upgrade helper requires the email python module, and if you try to run it on a machine which has the buildtools installed (and env script sourced, which you'd need to run builds) then it fails to run:

$ ./upgradehelper.py 
Traceback (most recent call last):
  File "./upgradehelper.py", line 47, in <module>
    from emailhandler import Email
  File "/home/paul/poky/auto-upgrade-helper/emailhandler.py", line 29, in <module>
    from smtplib import SMTP
  File "/opt/poky/1.7/sysroots/x86_64-pokysdk-linux/usr/lib/python2.7/smtplib.py", line 46, in <module>
    import email.utils
ImportError: No module named email.utils