fix: Removing Python 3.9 support due to EOL

PiperOrigin-RevId: 906558007

Author: yinghsienwu

.kokoro/continuous/unit.cfg

@@ -1,6 +1,6 @@
 # Format: //devtools/kokoro/config/proto/build.proto
 
-# Run all unit test sessions, in Python 3.7 to 3.9
+# Run all unit test sessions, in Python 3.10 to 3.13
 env_vars: {
     key: "NOX_SESSION"
     value: "unit"

.kokoro/docker/docs/Dockerfile

@@ -60,16 +60,16 @@ RUN apt-get update \
   && rm -rf /var/lib/apt/lists/* \
   && rm -f /var/cache/apt/archives/*.deb
 
-###################### Install python 3.9.13
+###################### Install python 3.10.20
 
-# Download python 3.9.13
-RUN wget https://www.python.org/ftp/python/3.9.13/Python-3.9.13.tgz
+# Download python 3.10.20
+RUN wget https://www.python.org/ftp/python/3.10.20/Python-3.10.20.tgz
 
 # Extract files
-RUN tar -xvf Python-3.9.13.tgz
+RUN tar -xvf Python-3.10.20.tgz
 
-# Install python 3.9.13
-RUN ./Python-3.9.13/configure --enable-optimizations
+# Install python 3.10.20
+RUN ./Python-3.10.20/configure --enable-optimizations
 RUN make altinstall
 
 ###################### Install pip
@@ -80,4 +80,4 @@ RUN wget -O /tmp/get-pip.py 'https://bootstrap.pypa.io/get-pip.py' \
 # Test pip
 RUN python3 -m pip
 
-CMD ["python3.9"]
+CMD ["python3.10"]

.kokoro/presubmit/release.cfg

@@ -3,7 +3,7 @@
 # Run system tests in presubmit for library releases
 env_vars: {
     key: "NOX_SESSION"
-    value: "system-3.9 unit"
+    value: "system-3.10 unit"
 }
 
 # Run system tests in parallel, splitting up by file