[BUG] boto_rds.subnet_group_present broken

Description

boto_rds.subnet_group_present no longer works on 3004 (it last worked for me on 3000.9 with Python 2.7)

Setup

Please be as specific as possible and give set-up details.

• on-prem machine
• VM (Virtualbox, KVM, etc. please specify)
• VM running on a cloud service, please be explicit and add details
• container (Kubernetes, Docker, containerd, etc. please specify)
• or a combination, please be explicit
• jails if it is FreeBSD

System boto packages:

python3-boto      2.44.0-1.1
python3-boto3     1.9.86-1
python3-botocore  1.12.103+repack-1

test_boto_subnet_group_present.sls:

test_subnet_group_creation:
  boto_rds.subnet_group_present:
    - region: us-east-2
    - name: test_subnet-group
    - description: test_subnet-group
    - subnet_names:
      - private-one_core_subnet
      - private-two_core_subnet

Steps to Reproduce the behavior

1. (Authentication is not an issue, other boto states work fine)
2. Apply test state:

   sudo salt-call state.apply test_boto_subnet_group_present
   

3. Get error:

   local:
   ----------
             ID: test_subnet_group_creation
       Function: boto_rds.subnet_group_present
         Result: False
        Comment: An exception occurred in this state: Traceback (most recent call last):
                   File "/usr/lib/python3/dist-packages/salt/modules/boto_rds.py", line 219, in subnet_group_exists
                     rds = conn.describe_db_subnet_groups(DBSubnetGroupName=name)
                   File "/usr/lib/python3/dist-packages/botocore/client.py", line 357, in _api_call
                     return self._make_api_call(operation_name, kwargs)
                   File "/usr/lib/python3/dist-packages/botocore/client.py", line 661, in _make_api_call
                     raise error_class(parsed_response, operation_name)
                 botocore.errorfactory.DBSubnetGroupNotFoundFault: An error occurred (DBSubnetGroupNotFoundFault) when calling the DescribeDBSubnetGroups operation: DB Subnet group 'test_subnet-group' not found.
                 
                 During handling of the above exception, another exception occurred:
                 
                 Traceback (most recent call last):
                   File "/usr/lib/python3/dist-packages/salt/state.py", line 2180, in call
                     *cdata["args"], **cdata["kwargs"]
                   File "/usr/lib/python3/dist-packages/salt/loader/lazy.py", line 149, in __call__
                     return self.loader.run(run_func, *args, **kwargs)
                   File "/usr/lib/python3/dist-packages/salt/loader/lazy.py", line 1201, in run
                     return self._last_context.run(self._run_as, _func_or_method, *args, **kwargs)
                   File "/usr/lib/python3/dist-packages/salt/loader/lazy.py", line 1216, in _run_as
                     return _func_or_method(*args, **kwargs)
                   File "/usr/lib/python3/dist-packages/salt/loader/lazy.py", line 1249, in wrapper
                     return f(*args, **kwargs)
                   File "/usr/lib/python3/dist-packages/salt/states/boto_rds.py", line 556, in subnet_group_present
                     name=name, tags=tags, region=region, key=key, keyid=keyid, profile=profile
                   File "/usr/lib/python3/dist-packages/salt/loader/lazy.py", line 149, in __call__
                     return self.loader.run(run_func, *args, **kwargs)
                   File "/usr/lib/python3/dist-packages/salt/loader/lazy.py", line 1201, in run
                     return self._last_context.run(self._run_as, _func_or_method, *args, **kwargs)
                   File "/usr/lib/python3/dist-packages/salt/loader/lazy.py", line 1216, in _run_as
                     return _func_or_method(*args, **kwargs)
                   File "/usr/lib/python3/dist-packages/salt/modules/boto_rds.py", line 222, in subnet_group_exists
                     if "DBSubnetGroupNotFoundFault" in e.message:
                 AttributeError: 'DBSubnetGroupNotFoundFault' object has no attribute 'message'
        Started: 20:06:01.866093
       Duration: 234.686 ms
        Changes:
   

Expected behavior

salt state should work as documented and as it did previously

Versions Report

Salt Version:
          Salt: 3004
 
Dependency Versions:
          cffi: Not Installed
      cherrypy: Not Installed
      dateutil: 2.7.3
     docker-py: Not Installed
         gitdb: 2.0.5
     gitpython: 2.1.11
        Jinja2: 2.10
       libgit2: Not Installed
      M2Crypto: Not Installed
          Mako: Not Installed
       msgpack: 0.5.6
  msgpack-pure: Not Installed
  mysql-python: Not Installed
     pycparser: Not Installed
      pycrypto: 2.6.1
  pycryptodome: 3.6.1
        pygit2: Not Installed
        Python: 3.7.3 (default, Jan 22 2021, 20:04:44)
  python-gnupg: Not Installed
        PyYAML: 3.13
         PyZMQ: 17.1.2
         smmap: 2.0.5
       timelib: Not Installed
       Tornado: 4.5.3
           ZMQ: 4.3.1
 
System Versions:
          dist: debian 10 buster
        locale: UTF-8
       machine: x86_64
       release: 4.19.0-18-amd64
        system: Linux
       version: Debian GNU/Linux 10 buster

Additional context

Based on https://github.com/fugue/credstash/issues/224#issuecomment-548553323, it seems like this is a Python 2 => Python 3 issue.

Potential solution:

--- boto_rds.py.76e5088	2022-01-31 20:34:20.477882216 +0000
+++ boto_rds.py.NEW	2022-01-31 20:30:32.830970932 +0000
@@ -219,7 +219,7 @@
         rds = conn.describe_db_subnet_groups(DBSubnetGroupName=name)
         return {"exists": bool(rds)}
     except ClientError as e:
-        if "DBSubnetGroupNotFoundFault" in e.message:
+        if "DBSubnetGroupNotFoundFault" in str(e):
             return {"exists": False}
         else:
             return {"error": __utils__["boto3.get_error"](e)}

This solution works for me, but maybe something like what parameter_group_exists() has would be better.