Add more test for bytearray.pop and fix the panic message

tests/snippets/bytearray.py

@@ -43,3 +43,12 @@ c = bytearray([123, 255, 111])
 assert len(c) == 3
 c.pop()
 assert len(c) == 2
+c.pop()
+c.pop()
+
+try:
+    c.pop()
+except IndexError:
+    pass
+else:
+    assert False

vm/src/obj/objbytes.rs

@@ -185,7 +185,7 @@ pub fn get_value<'a>(obj: &'a PyObjectRef) -> impl Deref<Target = Vec<u8>> + 'a
         if let PyObjectPayload::Bytes { ref value } = py_obj.payload {
             value
         } else {
-            panic!("Inner error getting int {:?}", obj);
+            panic!("Inner error getting bytearray {:?}", obj);
         }
     })
 }
@@ -195,7 +195,7 @@ pub fn get_mut_value<'a>(obj: &'a PyObjectRef) -> impl DerefMut<Target = Vec<u8>
         if let PyObjectPayload::Bytes { ref mut value } = py_obj.payload {
             value
         } else {
-            panic!("Inner error getting int {:?}", obj);
+            panic!("Inner error getting bytearray {:?}", obj);
         }
     })
 }