validators: add yaml parsing based on suffix

"JSON Schema" schemas are not only written in JSON but also in YAML, a
popular example is the Linux Kernel[0]. While it is possible to convert
any input file from YAML to JSON on the fly[1], the automatic resolving
of schema references is not possible.

To allow YAML files for the CLI tool of jsonschema, check the file
suffix and parse the referenced file as YAML if it ends on `yaml` or
`yml`. In case the Python library `pyyaml` is not installed or any other
suffix is found, parsing defaults to JSON as before.

[0]: https://github.com/torvalds/linux/tree/master/Documentation/devicetree/bindings
[1]: #582 (comment)

Signed-off-by: Paul Spooren <[email protected]>

Author: aparcar

jsonschema/tests/test_validators.py

@@ -1796,3 +1796,6 @@ class _ReallyFakeJSONResponse(object):
 
     def json(self):
         return json.loads(self._response)
+
+    def text(self):
+        return self._response

jsonschema/validators.py

@@ -837,18 +837,29 @@ def resolve_remote(self, uri):
         except ImportError:
             requests = None
 
+        try:
+            import yaml
+        except ImportError:
+            yaml = None
+
         scheme = urlsplit(uri).scheme
 
         if scheme in self.handlers:
             result = self.handlers[scheme](uri)
-        elif scheme in [u"http", u"https"] and requests:
-            # Requests has support for detecting the correct encoding of
-            # json over http
-            result = requests.get(uri).json()
         else:
-            # Otherwise, pass off to urllib and assume utf-8
-            with urlopen(uri) as url:
-                result = json.loads(url.read().decode("utf-8"))
+            path = urlsplit(uri).path
+            if scheme in [u"http", u"https"] and requests:
+                # Requests has support for detecting the correct encoding
+                received = requests.get(uri).text
+            else:
+                # Otherwise, pass off to urllib and assume utf-8
+                with urlopen(uri) as url:
+                    received = url.read().decode("utf-8")
+
+            if path.endswith((".yaml", ".yml")) and yaml:
+                result = yaml.safe_load(received)
+            else:
+                result = json.loads(received)
 
         if self.cache_remote:
             self.store[uri] = result