Fix doctests with Python 2

pyuca/utils.py

@@ -23,14 +23,14 @@ def int2hexstrings(number_list):
     >>> int2hexstrings([0, 1, 65535])
     ['0000', '0001', 'FFFF']
     """
-    return ["{:04X}".format(n) for n in number_list]
+    return [str("{:04X}".format(n)) for n in number_list]
 
 
 def format_collation_elements(collation_elements):
     """
     format collation element array (list of list of integer weights)
 
-    >>> format_collation_elements([[1, 2, 3], [4, 5]])
+    >>> str(format_collation_elements([[1, 2, 3], [4, 5]]))
     '[0001.0002.0003], [0004.0005]'
     >>> format_collation_elements(None)
     """
@@ -47,7 +47,7 @@ def format_collation_elements(collation_elements):
 def format_sort_key(sort_key):
     """
     format sort key (list of integers) with | level boundaries
-    >>> format_sort_key([1, 0, 65535])
+    >>> str(format_sort_key([1, 0, 65535]))
     '0001 | FFFF'
     """
     return " ".join(