safehasattr: pass attribute name as string instead of bytes

This is a step toward replacing `util.safehasattr` usage with plain `hasattr`.
The builtin function behave poorly in Python2 but this was fixed in Python3.

These change are done one by one as they tend to have a small odd to trigger
puzzling breackage.

mercurial/templateutil.py

@@ -307,7 +307,7 b' class hybrid(wrapped):'
         return hybriditem(None, key, val, self._makemap)
 
     def filter(self, context, mapping, select):
-        if util.safehasattr(self._values, b'get'):
+        if util.safehasattr(self._values, 'get'):
             values = {
                 k: v
                 for k, v in self._values.items()