commands: hg debuginstall checks missing templates (issue4151)

Missing templates where not reported as a problem, only an empty bracket
were shown as indication of no found template directory:
  $ hg debuginstall
  *...some lines*
  checking templates ()...
  *...some lines*
  no problems detected

Now the problem is reported and extended with some information. The style
of the messages is adapted to the other messages of debuginstall.

When no templates directories exist, it writes:
  $ hg debuginstall
  *...some lines*
  checking templates ()...
   no template directories found
   (templates seem to have been installed incorrectly)
  *...some lines*
  1 problems detected, please check your install!

When the template map is not found, it writes:
  $ hg debuginstall
  *...some lines*
  checking templates (/path/to/mercurial/templates)...
   template 'default' not found
   (templates seem to have been installed incorrectly)
  *...some lines*
  1 problems detected, please check your install!

When the template map is buggy the message is the same as before. The error
message is shown before the line "(templates seem ...)".


No test is added because testing this failure is complicated. It would
require to modify the templates directory of the mercurial installation,
or to monkey patch a function (os.listdir or any from mercurial.templater)
by a test extension.

mercurial/commands.py

@@ -2107,10 +2107,21 b' def debuginstall(ui):'
     import templater
     p = templater.templatepath()
     ui.status(_("checking templates (%s)...\n") % ' '.join(p))
+    if p:
+        m = templater.templatepath("map-cmdline.default")
+        if m:
+            # template found, check if it is working
     try:
-        templater.templater(templater.templatepath("map-cmdline.default"))
+                templater.templater(m)
     except Exception, inst:
         ui.write(" %s\n" % inst)
+                p = None
+        else:
+            ui.write(_(" template 'default' not found\n"))
+            p = None
+    else:
+        ui.write(_(" no template directories found\n"))
+    if not p:
         ui.write(_(" (templates seem to have been installed incorrectly)\n"))
         problems += 1