diff --git a/.travis.yml b/.travis.yml
index c1c9f6dda..24ea9cd1b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,9 +17,11 @@ before_install:
   - conda config --set always_yes yes --set changeps1 no
   - conda update -q conda
   - conda info -a
-  - conda create -q -n test-environment -c conda-forge python=$PYTHON_VERSION jupyter_server pytest==3.10.1 pytest-cov nodejs
+  - conda create -q -n test-environment -c conda-forge python=$PYTHON_VERSION jupyter_server pytest==3.10.1 pytest-cov nodejs flake8
   - source activate test-environment
 install:
   - pip install ".[test]"
+before_script:
+  - flake8 voila
 script:
   - py.test tests/
diff --git a/setup.cfg b/setup.cfg
index ed8a958e0..695dc1589 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -3,3 +3,6 @@ universal = 1
 
 [metadata]
 license_file = LICENSE
+
+[flake8]
+max-line-length=200
\ No newline at end of file
diff --git a/voila/__init__.py b/voila/__init__.py
index d2d6d9683..774fbee55 100644
--- a/voila/__init__.py
+++ b/voila/__init__.py
@@ -6,6 +6,7 @@
 # The full license is in the file LICENSE, distributed with this software.  #
 #############################################################################
 
+
 def _jupyter_nbextension_paths():
     return [dict(
         section="notebook",
diff --git a/voila/app.py b/voila/app.py
index c383a0497..9b0c1726d 100644
--- a/voila/app.py
+++ b/voila/app.py
@@ -7,13 +7,9 @@
 #############################################################################
 
 from zmq.eventloop import ioloop
-
-ioloop.install()
-
 import os
 import shutil
 import tempfile
-import json
 import logging
 import gettext
 
@@ -41,6 +37,7 @@
 from ._version import __version__
 from .static_file_handler import MultiStaticFileHandler
 
+ioloop.install()
 _kernel_id_regex = r"(?P<kernel_id>\w+-\w+-\w+-\w+-\w+)"
 
 
@@ -72,9 +69,7 @@ class Voila(Application):
         config=True,
         help='Will autoreload to server and the page when a template, js file or Python code changes'
     )
-    root_dir = Unicode(config=True,
-        help="The directory to use for notebooks."
-    )
+    root_dir = Unicode(config=True, help="The directory to use for notebooks.")
     static_root = Unicode(
         STATIC_ROOT,
         config=True,
@@ -107,8 +102,7 @@ class Voila(Application):
 
     @default('connection_dir_root')
     def _default_connection_dir(self):
-        return tempfile.gettempdir()
-        connection_dir = tempfile.mkdtemp()
+        connection_dir = tempfile.gettempdir()
         self.log.info('Using %s to store connection files' % connection_dir)
         return connection_dir
 
@@ -256,4 +250,5 @@ def listen(self):
         finally:
             shutil.rmtree(self.connection_dir)
 
+
 main = Voila.launch_instance
diff --git a/voila/handler.py b/voila/handler.py
index 2dee8bb69..6509ff268 100644
--- a/voila/handler.py
+++ b/voila/handler.py
@@ -10,7 +10,7 @@
 
 from jupyter_server.base.handlers import JupyterHandler
 
-import nbformat
+import nbformat  # noqa: F401
 from nbconvert.preprocessors.execute import executenb
 from nbconvert import HTMLExporter
 
@@ -87,4 +87,3 @@ def filter_empty_code_cells(cell):
         # Compose reply
         self.set_header('Content-Type', 'text/html')
         self.write(html)
-
diff --git a/voila/paths.py b/voila/paths.py
index 2ebb95e7a..8b14964c1 100644
--- a/voila/paths.py
+++ b/voila/paths.py
@@ -7,11 +7,13 @@
 #############################################################################
 
 import os
+import json
 from jupyter_core.paths import jupyter_path
 
 ROOT = os.path.dirname(__file__)
 STATIC_ROOT = os.path.join(ROOT, 'static')
 
+
 def collect_template_paths(
        nbconvert_template_paths,
        static_paths,
@@ -41,19 +43,19 @@ def collect_template_paths(
                     conf.get('base_template', 'default'))
 
             extra_nbconvert_path = os.path.join(dirname, 'nbconvert_templates')
-            #if not os.path.exists(extra_nbconvert_path):
+            # if not os.path.exists(extra_nbconvert_path):
             #    log.warning('template named %s found at path %r, but %s does not exist', template_name,
             #                dirname, extra_nbconvert_path)
             nbconvert_template_paths.insert(0, extra_nbconvert_path)
 
             extra_static_path = os.path.join(dirname, 'static')
-            #if not os.path.exists(extra_static_path):
+            # if not os.path.exists(extra_static_path):
             #    log.warning('template named %s found at path %r, but %s does not exist', template_name,
             #                dirname, extra_static_path)
             static_paths.insert(0, extra_static_path)
 
             extra_template_path = os.path.join(dirname, 'templates')
-            #if not os.path.exists(extra_template_path):
+            # if not os.path.exists(extra_template_path):
             #    log.warning('template named %s found at path %r, but %s does not exist', template_name,
             #                dirname, extra_template_path)
             template_paths.insert(0, extra_template_path)
@@ -62,5 +64,3 @@ def collect_template_paths(
             # given level of precedence (for instance user directory), we don't look further (for instance
             # in sys.prefix)
             break
-
-    return nbconvert_template_paths, static_paths, template_paths
diff --git a/voila/server_extension.py b/voila/server_extension.py
index 517a33f1c..71123fb5e 100644
--- a/voila/server_extension.py
+++ b/voila/server_extension.py
@@ -11,8 +11,6 @@
 
 from jinja2 import Environment, FileSystemLoader
 
-from jupyter_core.paths import jupyter_path
-
 from jupyter_server.utils import url_path_join
 from jupyter_server.base.handlers import path_regex
 from jupyter_server.base.handlers import FileFindHandler
diff --git a/voila/static_file_handler.py b/voila/static_file_handler.py
index 4726274f5..2ad58c6da 100644
--- a/voila/static_file_handler.py
+++ b/voila/static_file_handler.py
@@ -5,7 +5,7 @@
 
 class MultiStaticFileHandler(tornado.web.StaticFileHandler):
     """A static file handler that 'merges' a list of directories
-    
+
     If initialized like this::
 
         application = web.Application([
diff --git a/voila/treehandler.py b/voila/treehandler.py
index 79741b1b5..6cf96a48b 100644
--- a/voila/treehandler.py
+++ b/voila/treehandler.py
@@ -23,8 +23,8 @@ def generate_breadcrumbs(self, path):
         for i in range(len(parts)):
             if parts[i]:
                 link = url_path_join(self.base_url, 'voila/tree',
-                    url_escape(url_path_join(*parts[:i + 1])),
-                )
+                                     url_escape(url_path_join(*parts[:i + 1])),
+                                     )
                 breadcrumbs.append((link, parts[i]))
         return breadcrumbs
 
@@ -49,13 +49,12 @@ def get(self, path=''):
             page_title = self.generate_page_title(path)
             contents = cm.get(path)
             self.write(self.render_template('tree.html',
-                page_title=page_title,
-                notebook_path=path,
-                breadcrumbs=breadcrumbs,
-                contents=contents,
-                terminals_available=False,
-                server_root=self.settings['server_root_dir'],
-            ))
+                       page_title=page_title,
+                       notebook_path=path,
+                       breadcrumbs=breadcrumbs,
+                       contents=contents,
+                       terminals_available=False,
+                       server_root=self.settings['server_root_dir']))
         elif cm.file_exists(path):
             # it's not a directory, we have redirecting to do
             model = cm.get(path, content=False)