STY: Fix formatting

Author: bashtage

arch/tests/unitroot/test_unitroot.py

@@ -19,7 +19,7 @@
 
 try:
     from statsmodels.tsa.stattools import _autolag
-except:
+except ImportError:
     from statsmodels.tsa.stattools._stattools import _autolag
 
 from arch.unitroot import ADF, DFGLS, KPSS, PhillipsPerron, VarianceRatio, ZivotAndrews

arch/univariate/mean.py

@@ -949,7 +949,7 @@ def forecast(
                 "Due to backcasting and/or data availability start cannot be less "
                 "than the index of the largest value in the right-hand-side "
                 "variables used to fit the first observation.  In this model, "
-                "this value is {}.".format(max(0, earliest - 1))
+                f"this value is {max(0, earliest - 1)}."
             )
         # Parse params
         params = np.asarray(params)

arch/univariate/volatility.py

@@ -508,8 +508,7 @@ def _bootstrap_forecast(
         std_resid = resids / np.sqrt(sigma2)
         if start < self._min_bootstrap_obs:
             raise ValueError(
-                "start must include more than {} "
-                "observations".format(self._min_bootstrap_obs)
+                f"start must include more than {self._min_bootstrap_obs} observations"
             )
         rng = BootstrapRng(std_resid, start, random_state=random_state).rng()
         return self._simulation_forecast(