Some fixes from the futurize step 2.

common/python/nomadcore/local_backend.py

@@ -3,6 +3,7 @@ from future import standard_library
 standard_library.install_aliases()
 from builtins import range
 from builtins import object
+from builtins import str
 import numpy as np
 import io
 import logging
@@ -78,8 +79,8 @@ class LocalBackend(object):
 
             # Check that the value is actually of scalar type
             value_type = type(value)
-            if value_type not in [float, int, bool, type(b""), type(u""), np.float64]:
-                raise TypeError("The value '{}' for metainfo '{}' is not of scalar nature.".format(value, metaName))
+            if value_type not in [float, int, bool, type(b""), type(u""), str, np.float64]:
+                raise TypeError("The value '{}' with type '{}' for metainfo '{}' is not of scalar nature.".format(value, value_type, metaName))
 
             # Check that the metainfo should be scalar
             metainfo_shape = dataManager.metaInfo.shape
@@ -168,7 +169,7 @@ class LocalBackend(object):
         elif dtypeStr == "b":
             return [bool]
         elif dtypeStr == "C":
-            return [type(b""), type(u"")]
+            return [type(b""), type(u""), str]
         elif dtypeStr == "r":
             return [int]
         else: