docs: improve docs and update apache release scripts (#11457)

RELEASING/Dockerfile.from_local_tarball

@@ -14,7 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
-FROM python:3.7-jessie
+FROM python:3.7-buster
 
 RUN useradd --user-group --create-home --no-log-init --shell /bin/bash superset
 
@@ -56,7 +56,7 @@ RUN npm ci \
 
 WORKDIR /home/superset/apache-superset-incubating-$VERSION
 RUN pip install --upgrade setuptools pip \
-    && pip install -r requirements.txt \
+    && pip install -r requirements/base.txt \
     && pip install --no-cache-dir .
 
 RUN flask fab babel-compile --target superset/translations

RELEASING/Dockerfile.from_svn_tarball

@@ -14,7 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
-FROM python:3.7-jessie
+FROM python:3.7-buster
 
 RUN useradd --user-group --create-home --no-log-init --shell /bin/bash superset
 

RELEASING/Dockerfile.make_docs

@@ -14,7 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
-FROM python:3.7-jessie
+FROM python:3.7-buster
 ARG VERSION
 
 RUN git clone --depth 1 --branch ${VERSION} https://github.com/apache/incubator-superset.git /superset

RELEASING/Dockerfile.make_tarball

@@ -14,7 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
-FROM python:3.7-jessie
+FROM python:3.7-buster
 
 RUN apt-get update -y
 RUN apt-get install -y jq

RELEASING/README.md

@@ -65,11 +65,19 @@ the wrong files/using wrong names. There's a script to help you set correctly al
 necessary environment variables. Change your current directory to `superset/RELEASING`
 and execute the `set_release_env.sh` script with the relevant parameters:
 
+Usage (BASH):
 ```bash
-    # usage (BASH): . set_release_env.sh <SUPERSET_RC_VERSION> <PGP_KEY_FULLNAME>
-    # usage (ZSH): source set_release_env.sh <SUPERSET_RC_VERSION> <PGP_KEY_FULLNAME>
-    #
-    # example: source set_release_env.sh 0.37.0rc1 myid@apache.org
+    . set_release_env.sh <SUPERSET_RC_VERSION> <PGP_KEY_FULLNAME>
+```
+
+Usage (ZSH):
+```bash
+    source set_release_env.sh <SUPERSET_RC_VERSION> <PGP_KEY_FULLNAME>
+```
+
+Example:
+```bash
+    source set_release_env.sh 0.37.0rc1 myid@apache.org
 ```
 
 The script will output the exported variables. Here's example for 0.37.0rc1: