Slack provider does not install HTTP provider dependency

[cdabella]

Apache Airflow version: 2.1.1+astro.2

Kubernetes version: N/A

Environment: astro CLI local dev environment

Host

• Hardware configuration: AMD Ryzen 9 3900X (12-core, 3.8GHz), 32GB RAM, SSD
• OS: Windows 10 Pro 20H2
• Driver: Docker 20.10.7

Container

• OS: Debian 10 (buster)
• Kernel: Linux 971928acbe4c 4.19.128-microsoft-standard #1 SMP Tue Jun 23 12:58:10 UTC 2020 x86_64 GNU/Linux
• Install tools: astro CLI v0.25.4 (https://github.com/astronomer/astro-cli) deployed using astro dev start
• Others: Modify requirements.txt to include apache-airflow-providers-slack

What happened:
When importing the Slack Webhook operator, python throws a ModuleNotFoundError exception for the airflow.providers.http module.

$ python -c "import airflow.providers.slack.operators.slack_webhook"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/local/lib/python3.7/site-packages/airflow/providers/slack/operators/slack_webhook.py", line 21, in <module>
    from airflow.providers.http.operators.http import SimpleHttpOperator
ModuleNotFoundError: No module named 'airflow.providers.http'

What you expected to happen:
The module should import correctly, potentially with a DeprecationWarning

$ python -c "import airflow.providers.slack.operators.slack_webhook"
/usr/local/lib/python3.7/site-packages/airflow/providers/http/operators/http.py:26 DeprecationWarning: This decorator is deprecated.

In previous versions, all subclasses of BaseOperator must use apply_default decorator for the`default_args` feature to work properly.

In current version, it is optional. The decorator is applied automatically using the metaclass.

It appears that the module does not include apache-airflow-providers-http as a dependency.

$ pipdeptree -p apache-airflow-providers-slack</summary>
Warning!! Cyclic dependencies found:
* astronomer-certified => astronomer-airflow-version-check => astronomer-certified
* astronomer-airflow-version-check => astronomer-certified => astronomer-airflow-version-check
------------------------------------------------------------------------
apache-airflow-providers-slack==1!4.0.0
  - astronomer-certified [required: >=2.1.0, installed: 2.1.1.post2]
    [...]
  - slack-sdk [required: >=3.0.0,<4.0.0, installed: 3.7.0]

The missing dependency is also missing from the provider.yaml file.

How to reproduce it:

Non-functional SlackWebhookOperator

1. Add apache-airflow-providers-slack to the requirements.txt
2. Start the astro local dev environment with astro dev start
3. Add example-slack-dag.py file to the dags folder with the following code

from airflow.providers.slack.operators.slack_webhook import SlackWebhookOperator
from airflow import DAG
from airflow.operators.dummy_operator import DummyOperator
from datetime import datetime

from airflow.providers.slack.operators.slack_webhook import SlackWebhookOperator
from airflow import DAG
from airflow.operators.dummy_operator import DummyOperator

with DAG('slackwebhookoperator_import',
         start_date=datetime(2019, 1, 1),
         max_active_runs=3,
         schedule_interval=None,  # https://airflow.apache.org/docs/stable/scheduler.html#dag-runs
         # catchup=False # enable if you don't want historical dag runs to run
         ) as dag:

    t0 = DummyOperator(
        task_id='start'
    )

3. Observe DAG Import Error

Broken DAG: [/usr/local/airflow/dags/example-slack-dag.py] Traceback (most recent call last):
  File "/usr/local/airflow/dags/example-slack-dag.py", line 1, in <module>
    from airflow.providers.slack.operators.slack_webhook import SlackWebhookOperator
  File "/usr/local/lib/python3.7/site-packages/airflow/providers/slack/operators/slack_webhook.py", line 21, in <module>
    from airflow.providers.http.operators.http import SimpleHttpOperator
ModuleNotFoundError: No module named 'airflow.providers.http'

Functional SlackWebhookOperator

1. Add apache-airflow-providers-slack and apache-airflow-providers-http to the requirements.txt
2. Stop and start the local airflow environment with astro dev stop && astro dev start
3. Repeat step 3 from above, and observe no DAG Import Error.

Anything else we need to know: N/A

[boring-cyborg]

Thanks for opening your first issue here! Be sure to follow the issue template!

[potiuk]

Thanks for reporting it.

Http provider used to be preinstalled in 2.0 and it had been disabled due.to licensing issues. It has been restored as preinstalled provider and will be back in 2.1.3.

See #16974