1 files changed, 15 insertions, 14 deletions
diff --git a/setuptools/dist.py b/setuptools/dist.py
index 1e1b83be..f0f030b5 100644
--- a/setuptools/dist.py
+++ b/setuptools/dist.py
@@ -215,6 +215,10 @@ def check_importable(dist, attr, value):
 def assert_string_list(dist, attr, value):
     """Verify that value is a string list"""
     try:
+        # verify that value is a list or tuple to exclude unordered
+        # or single-use iterables
+        assert isinstance(value, (list, tuple))
+        # verify that elements of value are strings
         assert ''.join(value) != value
     except (TypeError, ValueError, AttributeError, AssertionError):
         raise DistutilsSetupError(
@@ -307,20 +311,17 @@ def check_test_suite(dist, attr, value):
 
 def check_package_data(dist, attr, value):
     """Verify that value is a dictionary of package names to glob lists"""
-    if isinstance(value, dict):
-        for k, v in value.items():
-            if not isinstance(k, str):
-                break
-            try:
-                iter(v)
-            except TypeError:
-                break
-        else:
-            return
-    raise DistutilsSetupError(
-        attr + " must be a dictionary mapping package names to lists of "
-        "wildcard patterns"
-    )
+    if not isinstance(value, dict):
+        raise DistutilsSetupError(
+            "{!r} must be a dictionary mapping package names to lists of "
+            "string wildcard patterns".format(attr))
+    for k, v in value.items():
+        if not isinstance(k, six.string_types):
+            raise DistutilsSetupError(
+                "keys of {!r} dict must be strings (got {!r})"
+                .format(attr, k)
+            )
+        assert_string_list(dist, 'values of {!r} dict'.format(attr), v)
 
 
 def check_packages(dist, attr, value):