Add Boto version check for tags parameter of cloudformation module

Tags parameter requires at least version 2.6.0 of Boto module. When tags
parameter is used with older version, error is raised. When tags
parameter is unused, module works as before.

cloud/cloudformation

@@ -63,6 +63,7 @@ options:
   tags:
     description:
       - Dictionary of tags to associate with stack and it's resources during stack creation. Cannot be updated later.
+        Requires at least Boto version 2.6.0.
     required: false
     default: null
     aliases: []
@@ -93,6 +94,7 @@ import json
 import time
 
 try:
+    import boto
     import boto.cloudformation.connection
 except ImportError:
     print "failed=True msg='boto required for this module'"
@@ -126,6 +128,17 @@ def boto_exception(err):
     return error
 
 
+def boto_version_required(version_tuple):
+    parts = boto.Version.split('.')
+    boto_version = []
+    try:
+        for part in parts:
+            boto_version.append(int(part))
+    except:
+        boto_version.append(-1)
+    return tuple(boto_version) >= tuple(version_tuple)
+
+
 def stack_operation(cfn, stack_name, operation):
     '''gets the status of a stack while it is created/updated/deleted'''
     existed = []
@@ -190,6 +203,11 @@ def main():
         elif 'EC2_REGION' in os.environ:
             r = os.environ['EC2_REGION']
 
+    kwargs = dict()
+    if tags is not None:
+        if not boto_version_required((2,6,0)):
+            module.fail_json(msg='Module parameter "tags" requires at least Boto version 2.6.0')
+        kwargs['tags'] = tags
 
 
     # convert the template parameters ansible passes into a tuple for boto
@@ -214,7 +232,7 @@ def main():
                              template_body=template_body,
                              disable_rollback=disable_rollback,
                              capabilities=['CAPABILITY_IAM'],
-                             tags=tags)
+                             **kwargs)
             operation = 'CREATE'
         except Exception, err:
             error_msg = boto_exception(err)