diff -r 6b3523f81f42 -r 26744ad37953 cubicweb/misc/migration/3.15.0_Any.py
--- a/cubicweb/misc/migration/3.15.0_Any.py	Fri Apr 05 17:21:14 2019 +0200
+++ b/cubicweb/misc/migration/3.15.0_Any.py	Fri Apr 05 17:58:19 2019 +0200
@@ -16,7 +16,7 @@
             sconfig.set_option(opt, val)
         except OptionError:
             continue
-    cfgstr = text_type(generate_source_config(sconfig), source._cw.encoding)
+    cfgstr = str(generate_source_config(sconfig), source._cw.encoding)
     source.cw_set(config=cfgstr)