diff --git a/nbviewer/app.py b/nbviewer/app.py
index 5e8b05a4..dc750d89 100644
--- a/nbviewer/app.py
+++ b/nbviewer/app.py
@@ -82,7 +82,6 @@ def nrfoot():
 
 
 class NBViewer(Application):
-
     name = Unicode("NBViewer")
 
     aliases = Dict(  # type: ignore
@@ -713,7 +712,6 @@ def init_tornado_application(self):
         self.tornado_application = web.Application(handlers, **settings)
 
     def init_logging(self):
-
         # Note that we inherit a self.log attribute from traitlets.config.Application
         # https://github.com/ipython/traitlets/blob/master/traitlets/config/application.py#L209
         # as well as a log_level attribute
diff --git a/nbviewer/providers/gist/handlers.py b/nbviewer/providers/gist/handlers.py
index fa7937ff..54b9a199 100644
--- a/nbviewer/providers/gist/handlers.py
+++ b/nbviewer/providers/gist/handlers.py
@@ -17,7 +17,6 @@
 
 
 class GistClientMixin(GithubClientMixin):
-
     # PROVIDER_CTX is a dictionary whose entries are passed as keyword arguments
     # to the render_template method of the GistHandler. The following describe
     # the information contained in each of these keyword arguments:
@@ -116,7 +115,6 @@ class GistHandler(GistClientMixin, RenderingHandler):
     """render a gist notebook, or list files if a multifile gist"""
 
     async def parse_gist(self, user, gist_id, filename=""):
-
         with self.catch_client_error():
             response = await self.github_client.get_gist(gist_id)
 
diff --git a/nbviewer/providers/github/handlers.py b/nbviewer/providers/github/handlers.py
index cf34ebf3..9c741514 100644
--- a/nbviewer/providers/github/handlers.py
+++ b/nbviewer/providers/github/handlers.py
@@ -26,7 +26,6 @@
 
 
 class GithubClientMixin:
-
     # PROVIDER_CTX is a dictionary whose entries are passed as keyword arguments
     # to the render_template method of the GistHandler. The following describe
     # the information contained in each of these keyword arguments:
diff --git a/nbviewer/tests/test_app.py b/nbviewer/tests/test_app.py
index 92ba8195..b55db810 100644
--- a/nbviewer/tests/test_app.py
+++ b/nbviewer/tests/test_app.py
@@ -4,6 +4,7 @@
 from subprocess import Popen
 from tempfile import NamedTemporaryFile
 
+
 # Also copied mostly from JupyterHub since again -- if not broken, don't fix.
 def test_generate_config():
     with NamedTemporaryFile(prefix="nbviewer_config", suffix=".py") as tf:
diff --git a/nbviewer/tests/test_config.py b/nbviewer/tests/test_config.py
index bc0a6152..e380f524 100644
--- a/nbviewer/tests/test_config.py
+++ b/nbviewer/tests/test_config.py
@@ -20,5 +20,4 @@ def get_server_cmd(cls):
 
 
 class TemplatePathEnvTestCase(NBViewerTestCase, CustomTemplateStub):
-
     environment_variables = {"NBVIEWER_TEMPLATE_PATH": tmpl_fixture}