Change minimum API version for exec_inspect

Author: zubron

docker/client.py

@@ -306,8 +306,8 @@ def exec_create(self, container, cmd, stdout=True, stderr=True, tty=False,
         return self._result(res, True)
 
     def exec_inspect(self, exec_id):
-        if utils.compare_version('1.15', self._version) < 0:
-            raise errors.InvalidVersion('Exec is not supported in API < 1.15')
+        if utils.compare_version('1.16', self._version) < 0:
+            raise errors.InvalidVersion('Exec is not supported in API < 1.16')
         if isinstance(exec_id, dict):
             exec_id = exec_id.get('Id')
         res = self._get(self._url("/exec/{0}/json".format(exec_id)))