diff --git a/scrapy/utils/misc.py b/scrapy/utils/misc.py
index a16d42eae..e72a5d042 100644
--- a/scrapy/utils/misc.py
+++ b/scrapy/utils/misc.py
@@ -1,15 +1,19 @@
 """Helper functions which doesn't fit anywhere else"""
-
 import re
 import hashlib
-
 from importlib import import_module
 from pkgutil import iter_modules
 
+import six
 from w3lib.html import remove_entities
+
 from scrapy.utils.python import flatten
 from scrapy.item import BaseItem
 
+
+_ITERABLE_SINGLE_VALUES = dict, BaseItem, six.text_type, bytes
+
+
 def arg_to_iter(arg):
     """Convert an argument to an iterable. The argument can be a None, single
     value, or an iterable.
@@ -18,11 +22,12 @@ def arg_to_iter(arg):
     """
     if arg is None:
         return []
-    elif not isinstance(arg, (dict, BaseItem)) and hasattr(arg, '__iter__'):
+    elif not isinstance(arg, _ITERABLE_SINGLE_VALUES) and hasattr(arg, '__iter__'):
         return arg
     else:
         return [arg]
 
+
 def load_object(path):
     """Load an object given its absolute object path, and return it.
 
@@ -48,6 +53,7 @@ def load_object(path):
 
     return obj
 
+
 def walk_modules(path, load=False):
     """Loads a module and all its submodules from a the given module path and
     returns them. If *any* module throws an exception while importing, that
@@ -69,6 +75,7 @@ def walk_modules(path, load=False):
                 mods.append(submod)
     return mods
 
+
 def extract_regex(regex, text, encoding='utf-8'):
     """Extract a list of unicode strings from the given text/encoding using the following policies:
 
@@ -91,12 +98,13 @@ def extract_regex(regex, text, encoding='utf-8'):
     else:
         return [remove_entities(unicode(s, encoding), keep=['lt', 'amp']) for s in strings]
 
+
 def md5sum(file):
     """Calculate the md5 checksum of a file-like object without reading its
     whole content in memory.
 
-    >>> from StringIO import StringIO
-    >>> md5sum(StringIO('file content to hash'))
+    >>> from io import BytesIO
+    >>> md5sum(BytesIO(b'file content to hash'))
     '784406af91dd5a54fbb9c84c2236595a'
     """
     m = hashlib.md5()
diff --git a/tests/py3-ignores.txt b/tests/py3-ignores.txt
index 6340ad683..685dbc17d 100644
--- a/tests/py3-ignores.txt
+++ b/tests/py3-ignores.txt
@@ -57,7 +57,6 @@ tests/test_toplevel.py
 tests/test_utils_defer.py
 tests/test_utils_iterators.py
 tests/test_utils_jsonrpc.py
-tests/test_utils_misc/__init__.py
 tests/test_utils_python.py
 tests/test_utils_reqser.py
 tests/test_utils_request.py