convert: improve exception reporting for SVN logstream

- catch all exceptions
- pickle a stringified version of the exception
- use a normal abort

Hopefully this will result in less mysterious convert exceptions

hgext/convert/subversion.py

@@ -106,11 +106,11 b' def get_log_child(fp, url, paths, start,'
                        discover_changed_paths,
                        strict_node_history,
                        receiver)
-    except SubversionException, (inst, num):
-        pickle.dump(num, fp, protocol)
     except IOError:
         # Caller may interrupt the iteration
         pickle.dump(None, fp, protocol)
+    except Exception, inst:
+        pickle.dump(str(inst), fp, protocol)
     else:
         pickle.dump(None, fp, protocol)
     fp.close()
@@ -145,7 +145,7 b' class logstream(object):'
             except:
                 if entry is None:
                     break
-                raise SubversionException("child raised exception", entry)
+                raise util.Abort(_("log stream exception '%s'") % entry)
             yield entry
 
     def close(self):