[library-web] mallard: fix handling of documents with emoji in titles

[Frederic Peters <fpeters src gnome org>]

commit 6b01f84b3bea5cafc7f2e4ef339d2d0e0110a636
Author: Frédéric Péters <fpeters 0d be>
Date:   Sat Sep 9 11:08:29 2017 +0200

    mallard: fix handling of documents with emoji in titles

 src/modtypes/mallard.py |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/modtypes/mallard.py b/src/modtypes/mallard.py
index 6c36137..72092ba 100644
--- a/src/modtypes/mallard.py
+++ b/src/modtypes/mallard.py
@@ -37,7 +37,7 @@ import errors
 from base import DocModule
 
 def dup_node(e):
-    return ET.fromstring(ET.tostring(e))
+    return ET.fromstring(ET.tostring(e, encoding='utf-8'))
 
 
 MAL_NS = 'http://projectmallard.org/1.0/'
@@ -189,7 +189,7 @@ class MallardCache:
 
     def dump(self, filename):
         tree = ET.ElementTree(self.toxml())
-        tree.write(filename)
+        tree.write(filename, encoding='utf-8')
 
 
 class MallardModule(DocModule):