Use an autofixture that monkeypatches read_file for both tests

tests/utils/test_jinja.py

@@ -21,30 +21,32 @@
 
 import os.path
 
+import pytest
+
 from qutebrowser.utils import jinja
 
 
-def _read_file(path):
+@pytest.fixture(autouse=True)
+def patch_read_file(monkeypatch):
+    def _read_file(path):
         """Mocked utils.read_file."""
         if path == os.path.join('html', 'test.html'):
             return """Hello {{var}}"""
         else:
             raise ValueError("Invalid path {}!".format(path))
 
+    monkeypatch.setattr('qutebrowser.utils.jinja.utils.read_file', _read_file)
 
-def test_simple_template(monkeypatch):
+
+def test_simple_template():
     """Test with a simple template."""
-    monkeypatch.setattr(
-        'qutebrowser.utils.jinja.utils.read_file',
-        _read_file
-    )
     template = jinja.env.get_template('test.html')
     # https://bitbucket.org/logilab/pylint/issue/490/
     data = template.render(var='World')  # pylint: disable=no-member
     assert data == "Hello World"
 
 
-def test_utf8(monkeypatch):
+def test_utf8():
     """Test rendering with an UTF8 template.
 
     This was an attempt to get a failing test case for #127 but it seems
@@ -52,10 +54,6 @@ def test_utf8(monkeypatch):
 
     https://github.com/The-Compiler/qutebrowser/issues/127
     """
-    monkeypatch.setattr(
-        'qutebrowser.utils.jinja.utils.read_file',
-        _read_file
-    )
     template = jinja.env.get_template('test.html')
     # https://bitbucket.org/logilab/pylint/issue/490/
     data = template.render(var='\u2603')  # pylint: disable=no-member