Use f-strings in the pr_monitor tool (#6208)

* pr_monitor - convert to f-strings to satisfy pylint consider-using-f-string

* clean up some redundant fixed strings concatenations

* also pin pytest-cov==3 to unblock CI coverage check which failed
  because pytest-cov==4.1.0 does not see line hits in a subprocess.

Finalizes #6171

cirq-core/cirq/_compat_test.py

@@ -781,8 +781,7 @@ def test_deprecated_module_deadline_validation():
 
 def _test_broken_module_1_inner():
     with pytest.raises(
-        DeprecatedModuleImportError,
-        match="missing_module cannot be imported. " "The typical reasons",
+        DeprecatedModuleImportError, match="missing_module cannot be imported. The typical reasons"
     ):
         # pylint: disable=unused-import
         import cirq.testing._compat_test_data.broken_ref as br  # type: ignore

cirq-core/cirq/qis/measures.py

@@ -211,7 +211,7 @@ def _numpy_arrays_to_state_vectors_or_density_matrices(
             state2.shape[0] if state2.ndim == 2 else np.prod(state2.shape, dtype=np.int64).item()
         )
         if dim1 != dim2:
-            raise ValueError('Mismatched dimensions in given states: ' f'{dim1} and {dim2}.')
+            raise ValueError(f'Mismatched dimensions in given states: {dim1} and {dim2}.')
         if qid_shape is None:
             qid_shape = (dim1,)
         else:

cirq-core/cirq/qis/states.py

@@ -314,7 +314,7 @@ def density_matrix(
         ValueError: Invalid density matrix.
     """
     if state.ndim != 2 or state.shape[0] != state.shape[1]:
-        raise ValueError('A density matrix must be a square matrix. ' f'Got shape {state.shape}.')
+        raise ValueError(f'A density matrix must be a square matrix. Got shape {state.shape}.')
     dim, _ = state.shape
     if qid_shape is None:
         qid_shape = _infer_qid_shape_from_dimension(dim)

cirq-google/cirq_google/calibration/engine_simulator.py

@@ -482,7 +482,6 @@ def _convert_to_circuit_with_drift(
     simulator: PhasedFSimEngineSimulator, circuit: cirq.AbstractCircuit
 ) -> cirq.Circuit:
     def map_func(op: cirq.Operation, _) -> cirq.Operation:
-
         if op.gate is None:
             raise IncompatibleMomentError(f'Operation {op} has a missing gate')
 
@@ -495,7 +494,7 @@ def map_func(op: cirq.Operation, _) -> cirq.Operation:
         translated = simulator.gates_translator(op.gate)
         if translated is None:
             raise IncompatibleMomentError(
-                f'Moment contains non-single qubit operation ' f'{op} with unsupported gate'
+                f'Moment contains non-single qubit operation {op} with unsupported gate'
             )
 
         a, b = op.qubits

cirq-google/cirq_google/engine/engine_program.py

@@ -550,7 +550,7 @@ def _deserialize_program(code: any_pb2.Any, program_num: Optional[int] = None) -
         batch = v2.batch_pb2.BatchProgram.FromString(code.value)
         if abs(program_num) >= len(batch.programs):
             raise ValueError(
-                f'Only {len(batch.programs)} in the batch but ' f'index {program_num} was specified'
+                f'Only {len(batch.programs)} in the batch but index {program_num} was specified'
             )
 
         program = batch.programs[program_num]

cirq-google/cirq_google/serialization/op_serializer.py

@@ -134,7 +134,7 @@ def to_proto(
         except KeyError as err:
             # Circuits must be serialized prior to any CircuitOperations that use them.
             raise ValueError(
-                'Encountered a circuit not in the constants table. ' f'Full error message:\n{err}'
+                f'Encountered a circuit not in the constants table. Full error message:\n{err}'
             )
 
         if (

dev_tools/modules.py

@@ -220,7 +220,7 @@ def _print_version():
 
 def _add_print_version_cmd(subparsers):
     print_version_cmd = subparsers.add_parser(
-        "print_version", help="Check that all module versions are the same, " "and print it."
+        "print_version", help="Check that all module versions are the same, and print it."
     )
     print_version_cmd.set_defaults(func=_print_version)