Looking at object.h the buffer interface is defined as 

/* buffer interface */
typedef struct bufferinfo {
    void *buf;
    PyObject *obj;        /* owned reference */
    Py_ssize_t len;
    Py_ssize_t itemsize;  /* This is Py_ssize_t so it can be
                             pointed to by strides in simple case.*/
    int readonly;
    int ndim;
    char *format;
    Py_ssize_t *shape;
    Py_ssize_t *strides;
    Py_ssize_t *suboffsets;
    Py_ssize_t smalltable[2];  /* static store for shape and strides of
                                  mono-dimensional buffers. */
    void *internal;
} Py_buffer;

typedef int (*getbufferproc)(PyObject *, Py_buffer *, int);
typedef void (*releasebufferproc)(PyObject *, Py_buffer *);

typedef struct {
     getbufferproc bf_getbuffer;
     releasebufferproc bf_releasebuffer;
} PyBufferProcs;

The code that's throwing that error looks like

if (pb == NULL || pb->bf_getbuffer == NULL) {
        PyErr_SetString(PyExc_TypeError,
                        "expected an object with the buffer interface");

I would argue that the error message gives appropriate information because it is expecting the object to have a bf_getbuffer member.

Maybe the friendly error message is best handled at a higher level?