python2.4: fix imports of sub-packages of the email package

These all have an obvious comment so if/when we finally ditch Python
2.4 we can eradicate them easily.

hgext/notify.py

@@ -134,6 +134,9 b' web.baseurl'
 '''
 
 import email, socket, time
+# On python2.4 you have to import this by name or they fail to
+# load. This was not a problem on Python 2.7.
+import email.Parser
 from mercurial.i18n import _
 from mercurial import patch, cmdutil, templater, util, mail
 import fnmatch

hgext/patchbomb.py

@@ -47,6 +47,11 b' hgrc(5) for details.'
 
 import os, errno, socket, tempfile, cStringIO
 import email
+# On python2.4 you have to import these by name or they fail to
+# load. This was not a problem on Python 2.7.
+import email.Generator
+import email.MIMEMultipart
+
 from mercurial import cmdutil, commands, hg, mail, patch, util
 from mercurial import scmutil
 from mercurial.i18n import _

mercurial/mail.py

@@ -9,6 +9,10 b' from i18n import _'
 import util, encoding, sslutil
 import os, smtplib, socket, quopri, time, sys
 import email
+# On python2.4 you have to import these by name or they fail to
+# load. This was not a problem on Python 2.7.
+import email.Header
+import email.MIMEText
 
 _oldheaderinit = email.Header.Header.__init__
 def _unifiedheaderinit(self, *args, **kw):

mercurial/patch.py

@@ -8,6 +8,10 b''
 
 import cStringIO, email, os, errno, re, posixpath
 import tempfile, zlib, shutil
+# On python2.4 you have to import these by name or they fail to
+# load. This was not a problem on Python 2.7.
+import email.Generator
+import email.Parser
 
 from i18n import _
 from node import hex, nullid, short