Turned out that if you used explicit relative import syntax

brettcannon · brettcannon · commit eb3cd301aea8 · 2010-05-20T18:37:55.000Z
(e.g. from .os import sep) and it failed, import would still try the implicit relative import semantics of an absolute import (from os import sep). That's not right, so when level is negative, only do explicit relative import semantics. Fixes issue #7902. Thanks to Meador Inge for the patch.
diff --git a/Lib/test/test_import.py b/Lib/test/test_import.py
@@ -431,6 +431,18 @@ def check_relative():
         self.assertRaises(ValueError, check_absolute)
         self.assertRaises(ValueError, check_relative)
 
+    def test_absolute_import_without_future(self):
+        # If absolute import syntax is used, then do not try to perform
+        # a relative import in the face of failure.
+        # Issue #7902.
+        try:
+            from .os import sep
+        except ImportError:
+            pass
+        else:
+            self.fail("explicit relative import triggered an "
+                      "implicit relative import")
+
 
 def test_main(verbose=None):
     run_unittest(ImportTests, PycRewritingTests, PathsTests, RelativeImportTests)
diff --git a/Misc/NEWS b/Misc/NEWS
@@ -12,6 +12,9 @@ What's New in Python 2.7 Release Candidate 1?
 Core and Builtins
 -----------------
 
+- Issue #7902: When using explicit relative import syntax, don't try
+  implicit relative import semantics.
+
 - Issue #7079: Fix a possible crash when closing a file object while using
   it from another thread.  Patch by Daniel Stutzbach.
 
diff --git a/Python/import.c b/Python/import.c
@@ -2134,7 +2134,8 @@ import_module_level(char *name, PyObject *globals, PyObject *locals,
     if (parent == NULL)
         return NULL;
 
-    head = load_next(parent, Py_None, &name, buf, &buflen);
+    head = load_next(parent, level < 0 ? Py_None : parent, &name, buf,
+                        &buflen);
     if (head == NULL)
         return NULL;
 
