convert: handle invalid subversion source paths

hgext/convert/subversion.py

@@ -278,7 +278,10 b' class svn_source(converter_source):'
             raise util.Abort(_('svn: start revision %s is not an integer')
                              % self.startrev)
 
+        try:
         self.head = self.latest(self.module, latest)
+        except SvnPathNotFound:
+            self.head = None
         if not self.head:
             raise util.Abort(_('no revision found in module %s')
                              % self.module)

tests/test-convert-svn-source.t

@@ -107,6 +107,11 b' Update svn repository again'
   Committed revision 8.
   $ cd ..
 
+  $ hg convert -s svn "$svnurl/non-existent-path" dest
+  initializing destination dest repository
+  abort: no revision found in module /proj B/non-existent-path
+  [255]
+
 ########################################
 
 Test incremental conversion