Fix use of user_data field with spot_price in ec2 module (#37628)

The user_data field is base64 encoded inside of the boto library.  In
Python3, base64 must be used with byte strings.  So we make sure to
encode the user_data into a byte string before passing it on to the boto
library.

Fixes #34978

lib/ansible/modules/cloud/amazon/ec2.py

@@ -541,15 +541,15 @@ EXAMPLES = '''
 
 '''
 
-import traceback
 import time
+import traceback
 from ast import literal_eval
-from ansible.module_utils.six import get_function_code, string_types
-from ansible.module_utils._text import to_text
+from distutils.version import LooseVersion
+
 from ansible.module_utils.basic import AnsibleModule
 from ansible.module_utils.ec2 import get_aws_connection_info, ec2_argument_spec, ec2_connect
-from distutils.version import LooseVersion
-from ansible.module_utils.six import string_types
+from ansible.module_utils.six import get_function_code, string_types
+from ansible.module_utils._text import to_bytes, to_text
 
 try:
     import boto.ec2
@@ -1042,7 +1042,7 @@ def create_instances(module, ec2, vpc, override_count=None):
                       'instance_type': instance_type,
                       'kernel_id': kernel,
                       'ramdisk_id': ramdisk,
-                      'user_data': user_data}
+                      'user_data': to_bytes(user_data, errors='surrogate_or_strict')}
 
             if ebs_optimized:
                 params['ebs_optimized'] = ebs_optimized