c7n-mailer: Can't subtract offset-naive and offset-aware datetimes

[nitrocode]

Describe the bug
When using the get_date_age jinja2 filter, I receive the error Can't subtract offset-naive and offset-aware datetimes

To Reproduce

1. Create a policy
2. Create a jinja template using get_date_age
3. Run the policy to create the sqs message
4. Run the mailer lambda to read the sqs message

The mailer should now show an exception

Expected behavior
A clear and concise description of what you expected to happen.

No errors

Background (please complete the following information):

• OS: [e.g. OSX 10.15]
• Python Version: python 3.8.1
• Custodian Version: 0.8.46.1
• Tool Version: c7n-mailer doesn't seem to have a --version switch...
• Cloud Provider: aws
• Policy:

vars:
  mode: &mode
    type: periodic
    schedule: "rate(7 days)"
    role: arn:aws:iam::{account_id}:role/cloud-custodian
    tags:
      application: cloud-custodian
      team: sre
      env: production

policies:
  - name: ami-unused
    description: |
      Unused AMIs older than a year
    resource: ami
    max-resources: 100
    mode:
      <<: *mode
    filters:
      - type: unused
        value: true
      - type: image-age
        days: 365
    actions:
      # - deregister
      - type: notify
        slack_template: ami-unused-slack
        to:
          - https://hooks.slack.com/
        transport:
          type: sqs
          queue: https://sqs.us-west-2.amazonaws.com/{account_id}/cloud-custodian

• Template:

{
  "attachments": [
    {
      "fallback": "Cloud Custodian Policy Violation",
      "title": "{{ policy['name'] }}",
      "color": "warning",
      "fields": [
        {
          "title": "Account",
          "value": "{{ account }}"
        },
        {
          "title": "Region",
          "value": "{{ region }}"
        },
        {
          "title": "Description",
          "value": "{{ policy['description'].strip() }}"
        },
        {
          "title": "Found",
          "value": "{{ resources | length }}"
        },
        {
          "title": "Subset",
          "value": "{%- for resource in (resources|sort(attribute='CreationDate'))[:5] -%}
                      {{ resource['ImageId'] }}, {% set age = (resource['CreationDate'] | date_time_format(format='%Y %b %d %H:%M %Z')) | get_date_age %}{{'%0.2f' % (age / 365)|float}} years, (tags: 
                      {%- for tag in resource['Tags'] -%}
                        {{ tag['Key'] }}={{ tag['Value'] }},
                      {%- endfor -%})\n\n
                    {%- endfor -%}"
        }
      ]
    }
  ],
  {% if recipient is string and not recipient.startswith('https://') %}
  "channel":"{{ recipient }}",
  {% endif -%}
  "username": "Custodian"
}

• Traceback:

  File "/var/task/jinja2/_compat.py", line 28, in reraise
    raise value.with_traceback(tb)
  File "msg-templates/ami-unused-slack.j2", line 32, in top-level template code
    {{ resource['ImageId'] }}, {% set age = (resource['CreationDate'] | date_time_format(format='%Y %b %d %H:%M %Z')) | get_date_age %}{{'%0.2f' % (age / 365)|float}} years, (tags:
  File "/var/task/c7n_mailer/utils.py", line 144, in get_date_age
    return (datetime.now(tz=tzutc()) - parser.parse(date)).days

Additional context
Add any other context about the problem here.

This works using replay.

c7n-mailer-replay \
    --config mailer.yml \
    -t templates \
    -p messages/sqs-ami-unused.slack.json

Possible fix for python2 or python3: https://stackoverflow.com/questions/796008/cant-subtract-offset-naive-and-offset-aware-datetimes

https://github.com/cloud-custodian/cloud-custodian/blob/master/tools/c7n_mailer/c7n_mailer/utils.py#L147