Handle predicates without __name__ in waitForEvent timeouts

mobly/controllers/android_device_lib/callback_handler.py

@@ -189,10 +189,11 @@ def waitForEvent(self, event_name, predicate, timeout=DEFAULT_TIMEOUT):
         break
       if predicate(event):
         return event
+    predicate_name = getattr(predicate, '__name__', repr(predicate))
     raise TimeoutError(
         self._ad,
         'Timed out after %ss waiting for an "%s" event that satisfies the '
-        'predicate "%s".' % (timeout, event_name, predicate.__name__),
+        'predicate "%s".' % (timeout, event_name, predicate_name),
     )
 
   def getAll(self, event_name):

mobly/snippet/callback_handler_base.py

@@ -233,10 +233,12 @@ def waitForEvent(
         return event
 
     custom_error = '' if message is None else f' Details: {message}.'
+    # Callables like functools.partial objects have no __name__.
+    predicate_name = getattr(predicate, '__name__', repr(predicate))
     raise errors.CallbackHandlerTimeoutError(
         self._device,
         f'Timed out after {timeout}s waiting for an "{event_name}" event that '
-        f'satisfies the predicate "{predicate.__name__}".{custom_error}',
+        f'satisfies the predicate "{predicate_name}".{custom_error}',
     )
 
   def getAll(self, event_name):

tests/mobly/snippet/callback_handler_base_test.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 """Unit tests for mobly.snippet.callback_handler_base.CallbackHandlerBase."""
 
+import functools
 import unittest
 from unittest import mock
 
@@ -190,6 +191,24 @@ def some_condition(_):
     ):
       handler.waitForEvent('AsyncTaskResult', some_condition, 0.01)
 
+  def test_wait_for_event_negative_with_partial_predicate(self):
+    handler = FakeCallbackHandler()
+    handler.mock_rpc_func.callEventWaitAndGetRpc = mock.Mock(
+        return_value=MOCK_RAW_EVENT
+    )
+
+    def has_secret_number(event, number):
+      return event.data['secretNumber'] == number
+
+    with self.assertRaisesRegex(
+        errors.CallbackHandlerTimeoutError, 'satisfies the predicate'
+    ):
+      handler.waitForEvent(
+          'AsyncTaskResult',
+          functools.partial(has_secret_number, number=42),
+          0.01,
+      )
+
   def test_wait_for_event_max_timeout(self):
     """waitForEvent should not raise the timeout exceed threshold error."""
     rpc_max_timeout_sec = 5