gdc: force utf-8 encoding of soap requests (#43963)

passerelle/apps/gdc/models.py

@@ -87,7 +87,12 @@ class Gdc(BaseResource):
 </%(action)s>
 </SOAP-ENV:Body>
 </SOAP-ENV:Envelope>""" % {'action': action, 'params': '\n'.join(params)}
-        resp = self.requests.post(self.service_url, data=data)
+        resp = self.requests.post(
+                self.service_url,
+                data=data.encode('utf-8'),
+                headers={'SOAPAction': '"%s"' % action,
+                         'Content-type': 'text/xml; charset=UTF-8'})
+
         return ET.ElementTree(ET.fromstring(resp.content))
 
     @endpoint()