feat: add python-runtime (#1496)

Signed-off-by: realanna <anna.reale@dynatrace.com>

python-runtime/Dockerfile

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+FROM python:3.9 AS production
+
+LABEL org.opencontainers.image.source="https://github.com/keptn/lifecycle-toolkit" \
+    org.opencontainers.image.url="https://keptn.sh" \
+    org.opencontainers.image.title="Keptn Python Runtime" \
+    org.opencontainers.image.vendor="Keptn" \
+    org.opencontainers.image.licenses="Apache-2.0"
+
+RUN pip install -q --disable-pip-version-check pyyaml GitPython requests
+
+COPY entrypoint.sh /entrypoint.sh
+
+USER 1000:1000
+
+ENV CMD_ARGS=""
+ENV SCRIPT=""
+
+ENTRYPOINT /entrypoint.sh

python-runtime/README.md

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+# Keptn Lifecycle Controller - Function Runtime
+
+## Build
+
+```shell
+docker build -t lifecycle-toolkit/python-runtime:${VERSION} .
+```
+
+## Usage
+
+The Keptn python runtime uses python3, and enables the follwing packages: requests, json, git, yaml
+
+The Keptn Lifecycle Toolkit uses this runtime to run [KeptnTask](https://lifecycle.keptn.sh/docs/tasks/write-tasks/)
+for pre- and post-checks.
+
+`KeptnTask`s can be tested locally with the runtime using the following commands.
+Replace `${VERSION}` with the KLT version of your choice.
+`SCRIPT` should refer to either a python file mounted locally in the container or to a url containing the file.
+
+### mounting a python file
+
+```shell
+docker run -v $(pwd)/samples/hellopy.py:/hellopy.py -e "SCRIPT=hellopy.py" -it lifecycle-toolkit/python-runtime:${VERSION}
+```
+
+Where the file in sample/hellopy.py contains python3 code:
+
+```python3
+import os
+
+print("Hello, World!")
+print(os.environ)
+```
+
+This should print in your shell, something like:
+
+```shell
+Hello, World!
+environ({'HOSTNAME': 'myhost', 'PYTHON_VERSION': '3.9.16', 'PWD': '/', 'CMD_ARGS': '','SCRIPT': 'hellopy.py', ...})
+```
+
+### Pass command line arguments to the python command
+
+You can pass python command line arguments by specifying `CMD_ARGS`.
+The following example will print the help of python3:
+
+```shell
+docker run -e "CMD_ARGS= -help" -it lifecycle-toolkit/python-runtime:${VERSION}
+```
+
+### Pass arguments to your python script
+
+In this example we pass one argument (-i test.txt) to the script
+
+```shell
+docker run -v $(pwd)/samples/args.py:/args.py -e "SCRIPT=args.py -i test.txt"  -it lifecycle-toolkit/python-runtime:${VERSION}
+```
+
+### Use a script from url
+
+We can call the hellopy.py script downloading it directly from github
+
+```shell
+docker run -e "SCRIPT=https://raw.githubusercontent.com/keptn/lifecycle-toolkit/main/python-runtime/samples/hellopy.py" -it lifecycle-toolkit/python-runtime:${VERSION}
+```
+
+<!-- markdownlint-disable-next-line MD033 MD013 -->
+<img referrerpolicy="no-referrer-when-downgrade" src="https://static.scarf.sh/a.png?x-pxid=858843d8-8da2-4ce5-a325-e5321c770a78" />

python-runtime/entrypoint.sh

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+#!/bin/bash
+
+set -eu
+
+regex='(https?|ftp|file)://[-[:alnum:]\+&@#/%?=~_|!:,.;]*[-[:alnum:]\+&@#/%=~_|]'
+
+if [[ $SCRIPT =~ $regex ]]
+then
+    curl -s $SCRIPT | python3 $CMD_ARGS -
+else
+    python3 $CMD_ARGS $SCRIPT
+fi

python-runtime/samples/args.py

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+import sys, getopt
+
+def main(argv):
+    inputfile = ''
+    opts, _ = getopt.getopt(argv,"i:",["ifile="])
+    for opt, arg in opts:
+        if opt in ("-i", "--ifile"):
+            inputfile = arg
+    print ('Input file is ', inputfile)
+
+if __name__ == "__main__":
+    main(sys.argv[1:])

python-runtime/samples/hellopy.py

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+import os
+
+print("Hello, World!")
+print(os.environ)