ref(py3): Remove SENTRY_PYTHON3 and -py3 versons (getsentry#764)

This is in preparation to make the PY3 version the default for Docker images and self-hosted. It is part **4/5**:

1. ~~Add `-py2` variants for the Python 2 build tags and introduce the `SENTRY_PYTHON2` env variable usage~~ (getsentry/sentry#22460)
2. ~~Switch getsentry/onpremise to Python 3 by default*, introducing the `SENTRY_PYTHON2` env var for Py2 builds via the `-py2` suffix~~ (getsentry#763)
3. ~~Move the unsuffixed version of the builds to Python 3~~ (getsentry/sentry#22466)
4. **Remove the `SENTRY_PYTHON3` env var support and `-py3` prefix usage from getsentry/onpremise**
5. Remove tagging of `-py3` builds from getsentry/sentry

.github/workflows/test.yml

@@ -32,7 +32,6 @@ jobs:
         env:
           COMPOSE_PARALLEL_LIMIT: 10
           SENTRY_PYTHON2: ${{ matrix.py2 == '1' || '' }}
-          SENTRY_PYTHON3: ${{ matrix.py2 != '1' || ''}}
         run: |
           ./install.sh
           ./test.sh

docker-compose.yml

@@ -8,7 +8,6 @@ x-sentry-defaults: &sentry_defaults
     args:
       - SENTRY_IMAGE
       - SENTRY_PYTHON2
-      - SENTRY_PYTHON3
   image: sentry-onpremise-local
   depends_on:
     - redis

install.sh

@@ -217,7 +217,7 @@ echo ""
 $dc pull -q --ignore-pull-failures 2>&1 | grep -v -- -onpremise-local || true
 
 # We may not have the set image on the repo (local images) so allow fails
-docker pull ${SENTRY_IMAGE}${SENTRY_PYTHON2:+-py2}${SENTRY_PYTHON3:+-py3} || true;
+docker pull ${SENTRY_IMAGE}${SENTRY_PYTHON2:+-py2} || true;
 
 echo ""
 echo "Building and tagging Docker images..."

sentry/Dockerfile

@@ -1,7 +1,6 @@
 ARG SENTRY_IMAGE
 ARG SENTRY_PYTHON2
-ARG SENTRY_PYTHON3
-FROM ${SENTRY_IMAGE}${SENTRY_PYTHON2:+-py2}${SENTRY_PYTHON3:+-py3}
+FROM ${SENTRY_IMAGE}${SENTRY_PYTHON2:+-py2}
 
 COPY . /usr/src/sentry