Rename style_guide.Error to style_guide.Violation

Move all Violation related methods from the StyleGuide to our Violation
class.

tests/unit/test_violation.py

@@ -0,0 +1,55 @@
+"""Tests for the flake8.style_guide.Violation class."""
+import mock
+import pytest
+
+from flake8 import style_guide
+
+
+@pytest.mark.parametrize('error_code,physical_line,expected_result', [
+    ('E111', 'a = 1', False),
+    ('E121', 'a = 1  # noqa: E111', False),
+    ('E121', 'a = 1  # noqa: E111,W123,F821', False),
+    ('E111', 'a = 1  # noqa: E111,W123,F821', True),
+    ('W123', 'a = 1  # noqa: E111,W123,F821', True),
+    ('E111', 'a = 1  # noqa: E11,W123,F821', True),
+    ('E111', 'a = 1  # noqa, analysis:ignore', True),
+    ('E111', 'a = 1  # noqa analysis:ignore', True),
+    ('E111', 'a = 1  # noqa - We do not care', True),
+    ('E111', 'a = 1  # noqa: We do not care', True),
+])
+def test_is_inline_ignored(error_code, physical_line, expected_result):
+    """Verify that we detect inline usage of ``# noqa``."""
+    error = style_guide.Violation(
+        error_code, 'filename.py', 1, 1, 'error text', None)
+    # We want `None` to be passed as the physical line so we actually use our
+    # monkey-patched linecache.getline value.
+
+    with mock.patch('linecache.getline', return_value=physical_line):
+        assert error.is_inline_ignored(False) is expected_result
+
+
+def test_disable_is_inline_ignored():
+    """Verify that is_inline_ignored exits immediately if disabling NoQA."""
+    error = style_guide.Violation(
+        'E121', 'filename.py', 1, 1, 'error text', 'line')
+
+    with mock.patch('linecache.getline') as getline:
+        assert error.is_inline_ignored(True) is False
+
+    assert getline.called is False
+
+
+@pytest.mark.parametrize('violation_file,violation_line,diff,expected', [
+    ('file.py', 10, {}, True),
+    ('file.py', 1, {'file.py': range(1, 2)}, True),
+    ('file.py', 10, {'file.py': range(1, 2)}, False),
+    ('file.py', 1, {'other.py': range(1, 2)}, False),
+    ('file.py', 10, {'other.py': range(1, 2)}, False),
+])
+def test_violation_is_in_diff(violation_file, violation_line, diff, expected):
+    """Verify that we find violations within a diff."""
+    violation = style_guide.Violation(
+        'E001', violation_file, violation_line, 1, 'warning', 'line',
+    )
+
+    assert violation.is_in(diff) is expected