sage.structure.debug_options should be cimported

src/sage/structure/category_object.pyx

@@ -60,7 +60,7 @@ from __future__ import print_function
 cimport generators
 cimport sage_object
 from sage.categories.category import Category
-from sage.structure.debug_options import debug
+from sage.structure.debug_options cimport debug
 from sage.misc.cachefunc import cached_method
 
 

src/sage/structure/debug_options.pxd

@@ -1,5 +1,6 @@
-
 cdef class DebugOptions_class:
     cdef public bint bad_parent_warnings
     cdef public bint unique_parent_warnings
     cdef public bint refine_category_hash_check
+
+cdef DebugOptions_class debug

src/sage/structure/debug_options.pyx

@@ -41,4 +41,14 @@ cdef class DebugOptions_class:
         self.refine_category_hash_check = False
 
 
-debug = DebugOptions_class()
+cdef DebugOptions_class debug = DebugOptions_class()
+
+# Since "debug" is declared with a type, it can only be cimported at
+# the Cython level, not imported in plain Python. So we add it to the
+# globals manually. We need to hack into Cython internals for this
+# since Sage is compiled with the old_style_globals option.
+from cpython.object cimport PyObject
+cdef extern from *:
+    PyObject* __pyx_d
+
+(<object>__pyx_d)["debug"] = debug

src/sage/structure/parent.pyx

@@ -108,7 +108,7 @@ from types import MethodType
 from .element cimport parent_c, coercion_model
 cimport sage.categories.morphism as morphism
 cimport sage.categories.map as map
-from sage.structure.debug_options import debug
+from sage.structure.debug_options cimport debug
 from sage.structure.sage_object cimport SageObject, rich_to_bool
 from sage.structure.misc import (dir_with_other_class, getattr_from_other_class,
                                  is_extension_type)