diff --git a/repo2docker/buildpacks/r.py b/repo2docker/buildpacks/r.py
index 8f92e0f01..7dd724e04 100644
--- a/repo2docker/buildpacks/r.py
+++ b/repo2docker/buildpacks/r.py
@@ -13,6 +13,7 @@
 # that seems to have a working IRKernel.
 RSPM_CUTOFF_DATE = datetime.date(2018, 12, 7)
 
+
 class RBuildPack(PythonBuildPack):
     """
     Setup R for use with a repository
@@ -270,9 +271,9 @@ def get_build_scripts(self):
         """
         if self.checkpoint_date < RSPM_CUTOFF_DATE:
             raise RuntimeError(
-                f'Microsoft killed MRAN, the source of R package snapshots before {RSPM_CUTOFF_DATE.strftime("%Y-%m-%d")}. '\
-                f'This repo has a snapshot date of {self.checkpoint_date.strftime("%Y-%m-%d")} specified in runtime.txt. '\
-                'Please use a newer snapshot date'
+                f'Microsoft killed MRAN, the source of R package snapshots before {RSPM_CUTOFF_DATE.strftime("%Y-%m-%d")}. '
+                f'This repo has a snapshot date of {self.checkpoint_date.strftime("%Y-%m-%d")} specified in runtime.txt. '
+                "Please use a newer snapshot date"
             )
 
         cran_mirror_url = self.get_rspm_snapshot_url(self.checkpoint_date)
diff --git a/tests/unit/test_r.py b/tests/unit/test_r.py
index d50295951..a7028d829 100644
--- a/tests/unit/test_r.py
+++ b/tests/unit/test_r.py
@@ -78,8 +78,11 @@ def test_mran_dead(tmpdir, base_image):
     tmpdir.chdir()
 
     with open("runtime.txt", "w") as f:
-        f.write('r-3.6-2017-06-04')
+        f.write("r-3.6-2017-06-04")
 
     r = buildpacks.RBuildPack(base_image)
-    with pytest.raises(RuntimeError, match=r'^Microsoft killed MRAN, the source of R package snapshots before 2018-12-07.*'):
-        r.get_build_scripts()
\ No newline at end of file
+    with pytest.raises(
+        RuntimeError,
+        match=r"^Microsoft killed MRAN, the source of R package snapshots before 2018-12-07.*",
+    ):
+        r.get_build_scripts()