remove v2/info call from Marathon client (#672)

We were using it to make sure we have a recent version of Marathon. Since
DC/OS CLI 0.4.0+ is only compatible with DC/OS 1.6.1, the Marathon
check is no longer necessary. It is also messing with ACLs since
v2/apps is at a user level and v2/info is an admin level.

cli/tests/integrations/test_marathon.py

@@ -675,7 +675,7 @@ def test_bad_configuration():
     config_set('marathon.url', 'http://localhost:88888')
 
     returncode, stdout, stderr = exec_command(
-        ['dcos', 'marathon', 'app', 'list'])
+        ['dcos', 'marathon', 'about'])
 
     assert returncode == 1
     assert stdout == b''

dcos/marathon.py

@@ -1,5 +1,4 @@
 import json
-from distutils.version import LooseVersion
 
 from dcos import config, http, util
 from dcos.errors import DCOSException, DCOSHTTPException
@@ -134,16 +133,6 @@ class Client(object):
         self._base_url = marathon_url
         self._timeout = timeout
 
-        min_version = "0.8.1"
-        version = LooseVersion(self.get_about()["version"])
-        self._version = version
-        if version < LooseVersion(min_version):
-            msg = ("The configured Marathon with version {0} is outdated. " +
-                   "Please use version {1} or later.").format(
-                       version,
-                       min_version)
-            raise DCOSException(msg)
-
     def _create_url(self, path):
         """Creates the url from the provided path.
         :param path: url path
@@ -154,14 +143,6 @@ class Client(object):
 
         return urllib.parse.urljoin(self._base_url, path)
 
-    def get_version(self):
-        """Get marathon version
-        :returns: marathon version
-        rtype: LooseVersion
-        """
-
-        return self._version
-
     def get_about(self):
         """Returns info about Marathon instance
 
@@ -702,23 +683,6 @@ class Client(object):
 
         return task
 
-    def get_app_schema(self):
-        """Returns app json schema
-
-        :returns: application json schema
-        :rtype: json schema or None if endpoint doesn't exist
-        """
-
-        version = self.get_version()
-        schema_version = LooseVersion("0.9.0")
-        if version < schema_version:
-            return None
-
-        url = self._create_url('v2/schemas/app')
-        response = _http_req(http.get, url, timeout=self._timeout)
-
-        return response.json()
-
     def normalize_app_id(self, app_id):
         """Normalizes the application id.