diff --git a/src/caosdb/connection/authentication/external_credentials_provider.py b/src/caosdb/connection/authentication/external_credentials_provider.py
index 8164d49b4d50203c4de4d1ecd946bb309e74dd4d..8795ee28789c775fd3e811f35f36d2f635b43f69 100644
--- a/src/caosdb/connection/authentication/external_credentials_provider.py
+++ b/src/caosdb/connection/authentication/external_credentials_provider.py
@@ -31,6 +31,7 @@ from .plain import PlainTextCredentialsProvider
 # meta class compatible with Python 2 *and* 3:
 ABC = ABCMeta(str('ABC'), (object, ), {str('__slots__'): ()})
 
+
 class ExternalCredentialsProvider(PlainTextCredentialsProvider, ABC):
     """ExternalCredentialsProvider.
 
diff --git a/src/caosdb/connection/authentication/interface.py b/src/caosdb/connection/authentication/interface.py
index fe9cb9170933cc12f76747d9d3c62a1a1fd2e8bd..b705ab130476ba5ab7b9459cbdda8e1a25ed8752 100644
--- a/src/caosdb/connection/authentication/interface.py
+++ b/src/caosdb/connection/authentication/interface.py
@@ -144,7 +144,6 @@ class AbstractAuthenticator(ABC):
             headers['Cookie'] = self._session_token
 
 
-
 class CredentialsAuthenticator(AbstractAuthenticator):
     """CredentialsAuthenticator
 
diff --git a/src/caosdb/exceptions.py b/src/caosdb/exceptions.py
index 485ad908b18310d9f8346beb2261b528a8a45cce..baa72b2428a42c75c3b0e8c46b55d5b11f843417 100644
--- a/src/caosdb/exceptions.py
+++ b/src/caosdb/exceptions.py
@@ -32,6 +32,7 @@ class CaosDBException(Exception):
         Exception.__init__(self, msg)
         self.msg = msg
 
+
 class ConfigurationException(CaosDBException):
     """ConfigurationException.
 
@@ -48,6 +49,7 @@ class ConfigurationException(CaosDBException):
     msg : str
         A description of the misconfiguration.
     """
+
     def __init__(self, msg):
         super(ConfigurationException, self).__init__(msg +
                                                      ConfigurationException._INFO)
diff --git a/unittests/test_authentication_external.py b/unittests/test_authentication_external.py
index c595d38f83f6994f62baca924b1225832b9a659b..a526385978bc6e356ae547e333768ccd6b26d5f9 100644
--- a/unittests/test_authentication_external.py
+++ b/unittests/test_authentication_external.py
@@ -10,9 +10,11 @@ from caosdb.connection.authentication import (
     external_credentials_provider as ecp
 )
 
+
 class _TestCaller(ecp.ExternalCredentialsProvider):
     pass
 
+
 def test_callback():
     def _callback(**config):
         assert "opt" in config
@@ -21,6 +23,7 @@ def test_callback():
     t.configure(opt=None)
     assert t.password == "secret"
 
+
 def test_log_password_incident():
     class _mylogger(logging.Logger):
         def log(self, level, msg, *args, **kwargs):
diff --git a/unittests/test_authentication_keyring.py b/unittests/test_authentication_keyring.py
index 721adefde1df3a819c72ec61433debd9856e6b9f..1105b9d29604e7809c1f6ab6d6a6d027c5115025 100644
--- a/unittests/test_authentication_keyring.py
+++ b/unittests/test_authentication_keyring.py
@@ -29,6 +29,7 @@ import sys
 from pytest import raises
 from caosdb.connection.authentication.keyring import KeyringCaller
 
+
 def test_initialization():
     def _callback(**config):
         assert not config
diff --git a/unittests/test_authentication_pass.py b/unittests/test_authentication_pass.py
index 968fdfd94b75eef27f76bb0e0f07370bca3e5150..e5e4870c890a6a19effe672a3fde127cb4ea1fd7 100644
--- a/unittests/test_authentication_pass.py
+++ b/unittests/test_authentication_pass.py
@@ -27,10 +27,11 @@ Tests for the caosdb.connection.authentication.pass module.
 """
 import sys
 from pytest import raises
-_PASSCALLER="caosdb.connection.authentication.pass"
+_PASSCALLER = "caosdb.connection.authentication.pass"
 __import__(_PASSCALLER)
 PassCaller = sys.modules[_PASSCALLER].PassCaller
 
+
 def test_initialization():
     def _callback(**config):
         assert not config
diff --git a/unittests/test_authentication_plain.py b/unittests/test_authentication_plain.py
index 6b59a23101111ee3592ee5395560a33ab1382b17..26c57e953f28a2a0ab80e35026c27ff74f18d370 100644
--- a/unittests/test_authentication_plain.py
+++ b/unittests/test_authentication_plain.py
@@ -30,6 +30,7 @@ from __future__ import unicode_literals
 from pytest import raises
 from caosdb.connection.authentication.plain import PlainTextCredentialsProvider
 
+
 def test_subclass_configure():
     """Test the correct passing of the password argument."""
     class SubClassOf(PlainTextCredentialsProvider):
@@ -53,6 +54,7 @@ def test_subclass_configure():
     assert exc_info.value.args[0] == ("configure() got multiple values for "
                                       "keyword argument 'password'")
 
+
 def test_plain_has_logger():
     p = PlainTextCredentialsProvider()
     assert hasattr(p, "logger")