Removed group_rank_object

pandas/_libs/groupby.pyx

@@ -130,14 +130,6 @@ def group_last_object(ndarray[object, ndim=2] out,
                 out[i, j] = resx[i, j]
 
 
-def group_rank_object(ndarray[float64_t, ndim=2] out,
-                      ndarray[object, ndim=2] values,
-                      ndarray[int64_t] labels,
-                      bint is_datetimelike, object ties_method,
-                      bint ascending, bint pct, object na_option):
-    raise ValueError("rank not supported for object dtypes")
-
-
 cdef inline float64_t median_linear(float64_t* a, int n) nogil:
     cdef int i, j, na_count = 0
     cdef float64_t result

pandas/tests/groupby/test_groupby.py

@@ -2038,8 +2038,7 @@ def test_rank_args_missing(self, grps, vals, ties_method, ascending,
     def test_rank_object_raises(self, ties_method, ascending, na_option,
                                 pct, vals):
         df = DataFrame({'key': ['foo'] * 5, 'val': vals})
-        with tm.assert_raises_regex(ValueError,
-                                    "rank not supported for object dtypes"):
+        with tm.assert_raises_regex(TypeError, "not callable"):
             df.groupby('key').rank(method=ties_method,
                                    ascending=ascending,
                                    na_option=na_option, pct=pct)