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diff --git a/third_party/python/yamllint/yamllint/rules/truthy.py b/third_party/python/yamllint/yamllint/rules/truthy.py
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+# -*- coding: utf-8 -*-
+# Copyright (C) 2016 Peter Ericson
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+Use this rule to forbid non-explictly typed truthy values other than allowed
+ones (by default: ``true`` and ``false``), for example ``YES`` or ``off``.
+
+This can be useful to prevent surprises from YAML parsers transforming
+``[yes, FALSE, Off]`` into ``[true, false, false]`` or
+``{y: 1, yes: 2, on: 3, true: 4, True: 5}`` into ``{y: 1, true: 5}``.
+
+.. rubric:: Options
+
+* ``allowed-values`` defines the list of truthy values which will be ignored
+  during linting. The default is ``['true', 'false']``, but can be changed to
+  any list containing: ``'TRUE'``, ``'True'``,  ``'true'``, ``'FALSE'``,
+  ``'False'``, ``'false'``, ``'YES'``, ``'Yes'``, ``'yes'``, ``'NO'``,
+  ``'No'``, ``'no'``, ``'ON'``, ``'On'``, ``'on'``, ``'OFF'``, ``'Off'``,
+  ``'off'``.
+* ``check-keys`` disables verification for keys in mappings. By default,
+  ``truthy`` rule applies to both keys and values. Set this option to ``false``
+  to prevent this.
+
+.. rubric:: Examples
+
+#. With ``truthy: {}``
+
+   the following code snippet would **PASS**:
+   ::
+
+    boolean: true
+
+    object: {"True": 1, 1: "True"}
+
+    "yes":  1
+    "on":   2
+    "True": 3
+
+     explicit:
+       string1: !!str True
+       string2: !!str yes
+       string3: !!str off
+       encoded: !!binary |
+                  True
+                  OFF
+                  pad==  # this decodes as 'N\xbb\x9e8Qii'
+       boolean1: !!bool true
+       boolean2: !!bool "false"
+       boolean3: !!bool FALSE
+       boolean4: !!bool True
+       boolean5: !!bool off
+       boolean6: !!bool NO
+
+   the following code snippet would **FAIL**:
+   ::
+
+    object: {True: 1, 1: True}
+
+   the following code snippet would **FAIL**:
+   ::
+
+    yes:  1
+    on:   2
+    True: 3
+
+#. With ``truthy: {allowed-values: ["yes", "no"]}``
+
+   the following code snippet would **PASS**:
+   ::
+
+    - yes
+    - no
+    - "true"
+    - 'false'
+    - foo
+    - bar
+
+   the following code snippet would **FAIL**:
+   ::
+
+    - true
+    - false
+    - on
+    - off
+
+#. With ``truthy: {check-keys: false}``
+
+   the following code snippet would **PASS**:
+   ::
+
+    yes:  1
+    on:   2
+    true: 3
+
+   the following code snippet would **FAIL**:
+   ::
+
+    yes:  Yes
+    on:   On
+    true: True
+"""
+
+import yaml
+
+from yamllint.linter import LintProblem
+
+
+TRUTHY = ['YES', 'Yes', 'yes',
+          'NO', 'No', 'no',
+          'TRUE', 'True', 'true',
+          'FALSE', 'False', 'false',
+          'ON', 'On', 'on',
+          'OFF', 'Off', 'off']
+
+
+ID = 'truthy'
+TYPE = 'token'
+CONF = {'allowed-values': list(TRUTHY), 'check-keys': bool}
+DEFAULT = {'allowed-values': ['true', 'false'], 'check-keys': True}
+
+
+def check(conf, token, prev, next, nextnext, context):
+    if prev and isinstance(prev, yaml.tokens.TagToken):
+        return
+
+    if (not conf['check-keys'] and isinstance(prev, yaml.tokens.KeyToken) and
+            isinstance(token, yaml.tokens.ScalarToken)):
+        return
+
+    if isinstance(token, yaml.tokens.ScalarToken):
+        if (token.value in (set(TRUTHY) - set(conf['allowed-values'])) and
+                token.style is None):
+            yield LintProblem(token.start_mark.line + 1,
+                              token.start_mark.column + 1,
+                              "truthy value should be one of [" +
+                              ", ".join(sorted(conf['allowed-values'])) + "]")