### What changes were proposed in this pull request?
This PR removes any dependencies on pypandoc. It also makes related tweaks to the docs README to clarify the dependency on pandoc (not pypandoc).
### Why are the changes needed?
We are using pypandoc to convert the Spark README from Markdown to ReST for PyPI. PyPI now natively supports Markdown, so we don't need pypandoc anymore. The dependency on pypandoc also sometimes causes issues when installing Python packages that depend on PySpark, as described in #18981.
### Does this PR introduce any user-facing change?
No.
### How was this patch tested?
Manually:
```sh
python -m venv venv
source venv/bin/activate
pip install -U pip
cd python/
python setup.py sdist
pip install dist/pyspark-3.0.0.dev0.tar.gz
pyspark --version
```
I also built the PySpark and R API docs with `jekyll` and reviewed them locally.
It would be good if a maintainer could also test this by creating a PySpark distribution and uploading it to [Test PyPI](https://test.pypi.org) to confirm the README looks as it should.
Closes#27376 from nchammas/SPARK-30665-pypandoc.
Authored-by: Nicholas Chammas <nicholas.chammas@liveramp.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
## What changes were proposed in this pull request?
Add [flake8](http://flake8.pycqa.org) tests to find Python syntax errors and undefined names.
__E901,E999,F821,F822,F823__ are the "_showstopper_" flake8 issues that can halt the runtime with a SyntaxError, NameError, etc. Most other flake8 issues are merely "style violations" -- useful for readability but they do not effect runtime safety.
* F821: undefined name `name`
* F822: undefined name `name` in `__all__`
* F823: local variable name referenced before assignment
* E901: SyntaxError or IndentationError
* E999: SyntaxError -- failed to compile a file into an Abstract Syntax Tree
## How was this patch tested?
$ __flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics__
$ __flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics__
Please review http://spark.apache.org/contributing.html before opening a pull request.
Closes#22266 from cclauss/patch-3.
Authored-by: cclauss <cclauss@bluewin.ch>
Signed-off-by: Holden Karau <holden@pigscanfly.ca>
## What changes were proposed in this pull request?
Not a big deal but this PR adds `sphinx` into `dev/requirements.txt` since we found it needed - https://github.com/apache/spark-website/pull/122#discussion_r200896018
## How was this patch tested?
manually:
```
pip install -r requirements.txt
```
Author: hyukjinkwon <gurwls223@apache.org>
Closes#21735 from HyukjinKwon/minor-dev.
## What changes were proposed in this pull request?
Fix instalation of mllib and ml sub components, and more eagerly cleanup cache files during test script & make-distribution.
## How was this patch tested?
Updated sanity test script to import mllib and ml sub-components.
Author: Holden Karau <holden@us.ibm.com>
Closes#16465 from holdenk/SPARK-19064-fix-pip-install-sub-components.
Minor since so few people use them, but it would probably be good to have a requirements file for our python release tools for easier setup (also version pinning).
cc JoshRosen who looked at the original JIRA.
Author: Holden Karau <holden@us.ibm.com>
Closes#10871 from holdenk/SPARK-10498-add-requirements-file-for-dev-python-tools.
