Revert "enable the email policy"

We're getting

  Traceback (most recent call last):
    File "/srv/ubuntu-archive/proposed-migration/code/b2/britney2/policies/email.py", line 171, in apply_policy_impl
      with smtplib.SMTP('localhost') as smtp:
  AttributeError: __exit__

  During handling of the above exception, another exception occurred:

  Traceback (most recent call last):
    File "/home/ubuntu-archive/proposed-migration/code/b2/britney.py", line 2892, in <module>
      Britney().main()
    File "/home/ubuntu-archive/proposed-migration/code/b2/britney.py", line 2860, in main
      self.write_excuses()
    File "/home/ubuntu-archive/proposed-migration/code/b2/britney.py", line 1680, in write_excuses
      if should_upgrade_src(pkg, 'unstable'):
    File "/home/ubuntu-archive/proposed-migration/code/b2/britney.py", line 1585, in should_upgrade_src
      v = policy.apply_policy(policy_info, suite, src, source_t, source_u, excuse)
    File "/srv/ubuntu-archive/proposed-migration/code/b2/britney2/policies/policy.py", line 103, in apply_policy
      return self.apply_policy_impl(pinfo, suite, source_name, source_data_tdist, source_data_srcdist, excuse)
    File "/srv/ubuntu-archive/proposed-migration/code/b2/britney2/policies/email.py", line 176, in apply_policy_impl
      except ConnectionRefusedError as err:
  NameError: global name 'ConnectionRefusedError' is not defined

on the production machine, which is currently running Python 3.2. It seems like smtplib.SMTP isn't a context manager in 3.2, and also ConnectionRefusedError doesn't exist there (it raises socket.error instead).

Robert's going to fix this, but for now let's go back to dry-run.

This reverts commit c05b687185.

britney.conf

@@ -102,4 +102,4 @@ ADT_PPAS          =
 ADT_SHARED_RESULTS_CACHE =
 
 # email uploaders for stuck uploads
-EMAIL_ENABLE     = yes
+EMAIL_ENABLE     = dry-run

britney_nobreakall.conf

@@ -100,4 +100,4 @@ ADT_PPAS          =
 ADT_SHARED_RESULTS_CACHE =
 
 # email uploaders for stuck uploads
-EMAIL_ENABLE     = yes
+EMAIL_ENABLE     = dry-run