Fix python2 unicode test error

I guess that if you don't have something python2 compliant to say. might as well say nothing at all
Also fix linter errors

tests/unit/conftest.py

@@ -1,7 +1,8 @@
-"""Shared fixtures between unit tests"""
-import pytest
+"""Shared fixtures between unit tests."""
 import optparse
 
+import pytest
+
 
 def options_from(**kwargs):
     """Generate a Values instances with our kwargs."""
@@ -14,5 +15,5 @@ def options_from(**kwargs):
 
 @pytest.fixture
 def default_options():
-    """Fixture returning the default options of flake8"""
+    """Fixture returning the default options of flake8."""
     return options_from()

tests/unit/test_file_checker.py

@@ -1,8 +1,8 @@
 """Unit tests for the FileChecker class."""
 import mock
 import pytest
-import flake8
 
+import flake8
 from flake8 import checker
 
 
@@ -48,8 +48,9 @@ def test_nonexistent_file():
 
 
 def test_raises_exception_on_failed_plugin(tmp_path, default_options):
+    """Checks that a failing plugin results in PluginExecutionFailed."""
     foobar = tmp_path / 'foobar.py'
-    foobar.write_text("I exist")
+    foobar.write_text(u"I exist!")  # Create temp file
     plugin = {
         "name": "failure",
         "plugin_name": "failure",  # Both are necessary