patchbomb: use modern pager to display -n/--test result (BC)

This should provide more consistent UX, but is a BC because the pager will
no longer be fired up for each message.

hgext/patchbomb.py

@@ -83,7 +83,6 b' from mercurial.i18n import _'
 from mercurial import (
     cmdutil,
     commands,
-    encoding,
     error,
     formatter,
     hg,
@@ -498,9 +497,7 b' def email(ui, repo, *revs, **opts):'
     With -n/--test, all steps will run, but mail will not be sent.
     You will be prompted for an email recipient address, a subject and
     an introductory message describing the patches of your patchbomb.
-    Then when all is done, patchbomb messages are displayed. If the
-    PAGER environment variable is set, your pager will be fired up once
-    for each patchbomb message, so you can verify everything is alright.
+    Then when all is done, patchbomb messages are displayed.
 
     In case email sending fails, you will find a backup of your series
     introductory message in ``.hg/last-email.txt``.
@@ -719,19 +716,14 b' def email(ui, repo, *revs, **opts):'
         if opts.get('test'):
             ui.status(_('displaying '), subj, ' ...\n')
             ui.flush()
-            if 'PAGER' in encoding.environ and not ui.plain():
-                fp = util.popen(encoding.environ['PAGER'], 'w')
-            else:
-                fp = ui
-            generator = emailmod.Generator.Generator(fp, mangle_from_=False)
+            ui.pager('email')
+            generator = emailmod.Generator.Generator(ui, mangle_from_=False)
             try:
                 generator.flatten(m, 0)
-                fp.write('\n')
+                ui.write('\n')
             except IOError as inst:
                 if inst.errno != errno.EPIPE:
                     raise
-            if fp is not ui:
-                fp.close()
         else:
             if not sendmail:
                 sendmail = mail.connect(ui, mbox=mbox)

tests/test-patchbomb-tls.t

@@ -10,10 +10,6 b' Set up SMTP server:'
   listening at localhost:$HGPORT
   $ cat a.pid >> $DAEMON_PIDS
 
-Ensure hg email output is sent to stdout:
-
-  $ unset PAGER
-
 Set up repository:
 
   $ hg init t

tests/test-patchbomb.t

@@ -28,9 +28,6 b' Mercurial-patchbomb/.* -> Mercurial-patc'
   $ echo "[extensions]" >> $HGRCPATH
   $ echo "patchbomb=" >> $HGRCPATH
 
-Ensure hg email output is sent to stdout
-  $ unset PAGER
-
   $ hg init t
   $ cd t
   $ echo a > a