Repository: apache/airflow

Issue:
Airflow v2.0.0b1 package doesnt include "api_connexion/exceptions"
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**Apache Airflow version**: 2.0.0b1


**Kubernetes version (if you are using kubernetes)** (use `kubectl version`): NA

**Environment**:

- **Cloud provider or hardware configuration**:
- **OS** (e.g. from /etc/os-release): macOS
- **Kernel** (e.g. `uname -a`):
- **Install tools**:
- **Others**:

**What happened**:
Installed apache-airlfow==2.0.0b1 using pip. 
Running `airflow webserver` gave the following error:
```
Traceback (most recent call last):
  File "/Users/abagri/Workspace/service-workflows/venv/bin/airflow", line 8, in <module>
    sys.exit(main())
  File "/Users/abagri/Workspace/service-workflows/venv/lib/python3.8/site-packages/airflow/__main__.py", line 40, in main
    args.func(args)
  File "/Users/abagri/Workspace/service-workflows/venv/lib/python3.8/site-packages/airflow/cli/cli_parser.py", line 49, in command
    func = import_string(import_path)
  File "/Users/abagri/Workspace/service-workflows/venv/lib/python3.8/site-packages/airflow/utils/module_loading.py", line 32, in import_string
    module = import_module(module_path)
  File "/usr/local/Cellar/python@3.8/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/Users/abagri/Workspace/service-workflows/venv/lib/python3.8/site-packages/airflow/cli/commands/webserver_command.py", line 43, in <module>
    from airflow.www.app import cached_app, create_app
  File "/Users/abagri/Workspace/service-workflows/venv/lib/python3.8/site-packages/airflow/www/app.py", line 39, in <module>
    from airflow.www.extensions.init_views import (
  File "/Users/abagri/Workspace/service-workflows/venv/lib/python3.8/site-packages/airflow/www/extensions/init_views.py", line 25, in <module>
    from airflow.api_connexion.exceptions import common_error_handler
ModuleNotFoundError: No module named 'airflow.api_connexion.exceptions'
```
<!-- (please include exact error messages if you can) -->

**What you expected to happen**:
Expect this command to start the webserver
<!-- What do you think went wrong? -->

**How to reproduce it**:
Install a fresh version of airflow, run `airflow db init` followed by `airflow webserver`
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**Anything else we need to know**:

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Discussion:
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cc: @ashb @kaxil  -> looking at it
I downloaded the packages externally from [here](https://pypi.org/project/apache-airflow/2.0.0b1/#files), this one also doesn't contain anything except the `openapi` folder.
> I downloaded the packages externally from [here](https://pypi.org/project/apache-airflow/2.0.0b1/#files), this one also doesn't contain anything except the `openapi` folder.

What command did you run? `pip install apache-airflow==2.0.0b1` or did you download the tar.gz and run `pip install FILEPATH_TO_TAR`
I first ran `pip install apache-airflow==2.0.0b1` and ran the command (airflow webserver) to get those errors.

Then to confirm, I downloaded the tar to check the contents. (didn't install the tar)
@ashb @kaxil -> indeed the problem is with implicit packages. The root cause is that `api_connexion` has no `__init__.py`
aah, we just need to add `__init__.py` file then, wonder why and how it got deleted / missing
It was never there - but the change with implicit packages, changed `find_namespace_packages` into `find_packages` in `setup.py` and now setup.py simply does not find the package.
It was there, it got renamed here: https://github.com/apache/airflow/commit/b2a28d1590410630d66966aa1f2b2a049a8c3b32 / https://github.com/apache/airflow/pull/12082


AAAAAH Github rebase magic finding wrong files!
Bad me!
Sounds like b2 then
@potiuk https://github.com/apache/airflow/pull/12082/files#r518885540

You also resolved this discussion of mine. This file rename was the cause of that problem.
Yeah, let's cut out beta2 today itself
b2? :(

Fix coming.

Resolving patch:
diff --git a/airflow/api_connexion/__init__.py b/airflow/api_connexion/__init__.py
new file mode 100644
--- /dev/null
+++ b/airflow/api_connexion/__init__.py
@@ -0,0 +1,16 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
diff --git a/docs/conf.py b/docs/conf.py
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -123,14 +123,6 @@
     "_api/airflow/providers/cncf/index.rst",
     # Packages without operators
     "_api/airflow/providers/sendgrid",
-    # Other API rst files.
-    "_api/endpoints/index.rst",
-    "_api/endpoints/*/index.rst",
-    "_api/exceptions/index.rst",
-    "_api/parameters/index.rst",
-    "_api/schemas/index.rst",
-    "_api/schemas/*/index.rst",
-    "_api/security/index.rst",
     # Templates or partials
     'autoapi_templates',
     'howto/operator/google/_partials',


Test patch: