Suggest Debian packages for some optional dependencies.

--- a/hgext/bugzilla.py
+++ b/hgext/bugzilla.py
@@ -421,7 +421,8 @@
         global MySQLdb
         MySQLdb = mysql
     except ImportError, err:
-        raise util.Abort(_('python mysql support not available: %s') % err)
+        raise util.Abort(_('python mysql support not available: %s') % err +
+                         _(' (try installing the %s package)') % 'python-mysqldb')
 
     if node is None:
         raise util.Abort(_('hook type %s does not pass a changeset id') %
--- a/hgext/convert/bzr.py
+++ b/hgext/convert/bzr.py
@@ -42,7 +42,8 @@
             # access bzrlib stuff
             branch
         except NameError:
-            raise NoRepo('Bazaar modules could not be loaded')
+            raise NoRepo('Bazaar modules could not be loaded' +
+                         _(' (try installing the %s package)') % 'bzr')
 
         path = os.path.abspath(path)
         self._checkrepotype(path)
--- a/hgext/convert/common.py
+++ b/hgext/convert/common.py
@@ -26,11 +26,12 @@
 
 class MissingTool(Exception): pass
 
-def checktool(exe, name=None, abort=True):
+def checktool(exe, name=None, abort=True, debname=None):
     name = name or exe
     if not util.find_exe(exe):
         exc = abort and util.Abort or MissingTool
-        raise exc(_('cannot find required "%s" tool') % name)
+        raise exc(_('cannot find required "%s" tool') % name +
+                  (debname and _(' (try installing the %s package)') % debname or ''))
 
 class NoRepo(Exception): pass
 
--- a/hgext/convert/cvs.py
+++ b/hgext/convert/cvs.py
@@ -21,7 +21,7 @@
         if not os.path.exists(cvs):
             raise NoRepo("%s does not look like a CVS checkout" % path)
 
-        checktool('cvs')
+        checktool('cvs', debname='cvs')
 
         self.changeset = None
         self.files = {}
--- a/hgext/convert/darcs.py
+++ b/hgext/convert/darcs.py
@@ -35,14 +35,15 @@
         if not os.path.exists(os.path.join(path, '_darcs')):
             raise NoRepo("%s does not look like a darcs repo" % path)
 
-        checktool('darcs')
+        checktool('darcs', debname='darcs')
         version = self.run0('--version').splitlines()[0].strip()
         if version < '2.1':
             raise util.Abort(_('darcs version 2.1 or newer needed (found %r)') %
                              version)
 
         if ElementTree is None:
-            raise util.Abort(_("Python ElementTree module is not available"))
+            raise util.Abort(_("Python ElementTree module is not available") +
+                             _(" (try installing the %s package)") % 'python-celementtree')
 
         self.path = os.path.realpath(path)
 
--- a/hgext/convert/git.py
+++ b/hgext/convert/git.py
@@ -37,7 +37,7 @@
         if not os.path.exists(path + "/objects"):
             raise NoRepo("%s does not look like a Git repo" % path)
 
-        checktool('git', 'git')
+        checktool('git', 'git', debname='git-core')
 
         self.path = path
 
--- a/hgext/convert/gnuarch.py
+++ b/hgext/convert/gnuarch.py
@@ -41,7 +41,8 @@
             if util.find_exe('tla'):
                 self.execmd = 'tla'
             else:
-                raise util.Abort(_('cannot find a GNU Arch tool'))
+                raise util.Abort(_('cannot find a GNU Arch tool') +
+                                 _(' (try installing the %s package)') % 'tla')
 
         commandline.__init__(self, ui, self.execmd)
 
--- a/hgext/convert/monotone.py
+++ b/hgext/convert/monotone.py
@@ -55,7 +55,7 @@
         self.files = None
         self.dirs  = None
 
-        checktool('mtn', abort=False)
+        checktool('mtn', abort=False, debname='monotone')
 
         # test if there are any revisions
         self.rev = None
--- a/hgext/convert/subversion.py
+++ b/hgext/convert/subversion.py
@@ -21,6 +21,7 @@
 
 from common import NoRepo, MissingTool, commit, encodeargs, decodeargs
 from common import commandline, converter_source, converter_sink, mapfile
+from common import checktool
 
 try:
     from svn.core import SubversionException, Pool
@@ -212,16 +213,19 @@
         try:
             SubversionException
         except NameError:
-            raise MissingTool(_('Subversion python bindings could not be loaded'))
+            raise MissingTool(_('Subversion python bindings could not be loaded') +
+                              _(' (try installing the %s package)') % 'python-subversion')
 
         try:
             version = svn.core.SVN_VER_MAJOR, svn.core.SVN_VER_MINOR
             if version < (1, 4):
                 raise MissingTool(_('Subversion python bindings %d.%d found, '
-                                    '1.4 or later required') % version)
+                                    '1.4 or later required') % version +
+                                  _(' (try upgrading the %s package)') % 'python-subversion')
         except AttributeError:
             raise MissingTool(_('Subversion python bindings are too old, 1.4 '
-                                'or later required'))
+                                'or later required') +
+                              _(' (try upgrading the %s package)') % 'python-subversion')
 
         self.lastrevs = {}
 
@@ -952,6 +956,9 @@
         return self.join('hg-authormap')
 
     def __init__(self, ui, path):
+        checktool('svn', debname='subversion')
+        checktool('svnadmin', debname='subversion')
+
         converter_sink.__init__(self, ui, path)
         commandline.__init__(self, ui, 'svn')
         self.delete = []
--- a/mercurial/hgweb/server.py
+++ b/mercurial/hgweb/server.py
@@ -260,7 +260,8 @@
                     from OpenSSL import SSL
                     ctx = SSL.Context(SSL.SSLv23_METHOD)
                 except ImportError:
-                    raise util.Abort(_("SSL support is unavailable"))
+                    raise util.Abort(_("SSL support is unavailable") +
+                                     _(" (try installing the %s package)") % 'python-openssl')
                 ctx.use_privatekey_file(ssl_cert)
                 ctx.use_certificate_file(ssl_cert)
                 sock = socket.socket(self.address_family, self.socket_type)