Bump pylint version to the latest release (#577)

This commit bumps the pylint version we use for CI and local style
enforcement to be the latest release 2.8.2 and updates the code so that
the new pylint version passes. One place to note is a new rule looking
for potentially unbalanced tuple rule is disabled because the number of
values in the return tuple from the rb circuit generator varies
depending on the input (so we can't fix the code to pass the rule.
The version we were using was missing python 3.9 support and causes issues
for anyone running locally with python 3.9. This fixes this so we can
run pylint with all supported versions of python.

constraints.txt

@@ -1,5 +1,5 @@
-pylint==2.4.4
-astroid==2.3.3
+pylint==2.8.2
+astroid==2.5.6
 pywin32==225
 setuptools==49.6.0
 pyfakefs==4.1.0

qiskit/ignis/measurement/discriminator/discriminators.py

@@ -286,10 +286,10 @@ def _scale_data(self, xdata: List[List[float]],
 
         try:
             from sklearn.preprocessing import StandardScaler
-        except ImportError:
+        except ImportError as exc:
             raise ImportError("To scale the xdata scikit-learn must be "
                               "installed. This can be done with 'pip install "
-                              "scikit-learn'")
+                              "scikit-learn'") from exc
 
         if not self._scaler or refit:
             self._scaler = StandardScaler(with_std=True)

qiskit/ignis/measurement/discriminator/filters.py

@@ -125,9 +125,9 @@ def get_base(expected_states: dict):
             for char in expected_states[key]:
                 try:
                     value = int(char)
-                except ValueError:
+                except ValueError as exc:
                     raise QiskitError('Cannot parse character in ' +
-                                      expected_states[key])
+                                      expected_states[key]) from exc
 
                 base = base if base > value else value
 

qiskit/ignis/measurement/discriminator/iq_discriminators.py

@@ -275,9 +275,9 @@ def plot(self, axs=None,
                 zz = np.array(zz).astype(float).reshape(xx.shape)
                 axs[0].contourf(xx, yy, zz, alpha=.2)
 
-            except ValueError:
+            except ValueError as exc:
                 raise QiskitError('Cannot convert expected state labels to '
-                                  'float.')
+                                  'float.') from exc
 
         n_qubits = len(self._qubit_mask)
         if show_fitting_data:

qiskit/ignis/mitigation/expval/complete_mitigator.py

@@ -154,8 +154,8 @@ def assignment_matrix(self, qubits: List[int] = None) -> np.ndarray:
             qubits = [qubits]
 
         # Compute marginal matrix
-        axis = tuple([self._num_qubits - 1 - i for i in set(
-            range(self._num_qubits)).difference(qubits)])
+        axis = tuple(self._num_qubits - 1 - i for i in set(
+            range(self._num_qubits)).difference(qubits))
         num_qubits = len(qubits)
         new_amat = np.zeros(2 * [2 ** num_qubits], dtype=float)
         for i, col in enumerate(self._assignment_mat.T[self._keep_indexes(qubits)]):

qiskit/ignis/verification/accreditation/fitters.py

@@ -111,5 +111,4 @@ def bound_variation_distance(self, theta):
             self.bound = self.bound/(self.N_acc/self.num_runs-theta)
             self.bound = self.bound+1-self.g_num
             self.confidence = 1-2*np.exp(-2*theta*self.num_runs*self.num_runs)
-        if self.bound > 1:
-            self.bound = 1
+        self.bound = min(self.bound, 1)

qiskit/ignis/version.py

@@ -12,6 +12,8 @@
 # copyright notice, and modified files need to carry a notice indicating
 # that they have been altered from the originals.
 
+# pylint: disable=consider-using-with
+
 """Functions for getting version information about ignis."""
 
 

requirements-dev.txt

@@ -1,4 +1,4 @@
-pylint==2.4.4
+pylint==2.8.2
 pycodestyle
 qiskit-aer>=0.3.0
 scikit-learn>=0.17

test/rb/generate_data.py

@@ -11,6 +11,9 @@
 # Any modifications or derivative works of this code must retain this
 # copyright notice, and modified files need to carry a notice indicating
 # that they have been altered from the originals.
+
+# pylint: disable=unbalanced-tuple-unpacking
+
 """
 Generate data for rb fitters tests
 """

test/rb/test_rb.py

@@ -13,6 +13,7 @@
 # that they have been altered from the originals.
 
 # pylint: disable=undefined-loop-variable,invalid-name,missing-type-doc
+# pylint: disable=unbalanced-tuple-unpacking
 
 """
 Run through RB for different qubit numbers to check that it's working