Fixed bug in deepcopy of IBMBackend (#658)

* Fixed recursion in deepcopy of IBMBackend.

* Release note

---------

Co-authored-by: Kevin Tian <kevin.tian@ibm.com>

qiskit_ibm_provider/ibm_backend.py

@@ -231,7 +231,7 @@ def __getattr__(self, name: str) -> Any:
         does not yet exist on IBMBackend class.
         """
         # Prevent recursion since these properties are accessed within __getattr__
-        if name in ["_properties", "_defaults", "_target"]:
+        if name in ["_properties", "_defaults", "_target", "_configuration"]:
             raise AttributeError(
                 "'{}' object has no attribute '{}'".format(
                     self.__class__.__name__, name

releasenotes/notes/backend_deepcopy-032282246b52e391.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixed infinite recursion when attempting to deepcopy an IBMBackend.
+

test/unit/test_backend.py

@@ -11,7 +11,7 @@
 # that they have been altered from the originals.
 
 """Tests for the backend functions."""
-
+import copy
 from datetime import datetime
 from unittest import mock
 import warnings
@@ -318,3 +318,9 @@ def test_multi_openqasm3_submission(self):
             backend.run(circuits=qasm3_circs, dynamic=True)
 
         mock_run.assert_called_once()
+
+    def test_deepcopy(self):
+        """Test that deepcopy of a backend works properly"""
+        backend = self._create_dc_test_backend()
+        backend_copy = copy.deepcopy(backend)
+        self.assertEqual(backend_copy.name, backend.name)