Bump python minimum version to 3.8

Also, switch ci_native_qt5 to g++-9 (from g++-8) to work around bugs.
This should be fine, because the i686_centos task still checks for g++-8
compatibility.

See
https://github.com/bitcoin/bitcoin/pull/27483#issuecomment-1513477050
for the list of bugs.

.cirrus.yml

@@ -228,7 +228,7 @@ task:
     PACKAGE_MANAGER_INSTALL: "yum install -y"
 
 task:
-  name: '[previous releases, uses qt5 dev package and some depends packages, DEBUG] [unsigned char] [buster]'
+  name: '[previous releases, qt5 dev package and depends packages, DEBUG] [focal]'
   previous_releases_cache:
     folder: "releases"
   << : *GLOBAL_TASK_TEMPLATE

.python-version

@@ -1 +1 @@
-3.7.16
+3.8.16

ci/test/00_setup_env_i686_centos.sh

@@ -8,7 +8,8 @@ export LC_ALL=C.UTF-8
 
 export HOST=i686-pc-linux-gnu
 export CONTAINER_NAME=ci_i686_centos
-export CI_IMAGE_NAME_TAG=quay.io/centos/centos:stream8
+export CI_IMAGE_NAME_TAG="quay.io/centos/centos:stream8"
+# Use minimum supported python3.8 and gcc-8, see doc/dependencies.md
 export CI_BASE_PACKAGES="gcc-c++ glibc-devel.x86_64 libstdc++-devel.x86_64 glibc-devel.i686 libstdc++-devel.i686 ccache libtool make git python38 python38-pip which patch lbzip2 xz procps-ng dash rsync coreutils bison"
 export PIP_PACKAGES="pyzmq"
 export GOAL="install"

ci/test/00_setup_env_native_nowallet_libbitcoinkernel.sh

@@ -7,8 +7,8 @@
 export LC_ALL=C.UTF-8
 
 export CONTAINER_NAME=ci_native_nowallet_libbitcoinkernel
-export CI_IMAGE_NAME_TAG=ubuntu:focal
-# Use minimum supported python3.7 (or python3.8, as best-effort) and clang-8, see doc/dependencies.md
+export CI_IMAGE_NAME_TAG="ubuntu:20.04"
+# Use minimum supported python3.8 and clang-8, see doc/dependencies.md
 export PACKAGES="python3-zmq clang-8 llvm-8 libc++abi-8-dev libc++-8-dev"
 export DEP_OPTS="NO_WALLET=1 CC=clang-8 CXX='clang++-8 -stdlib=libc++'"
 export GOAL="install"

ci/test/00_setup_env_native_qt5.sh

@@ -7,10 +7,10 @@
 export LC_ALL=C.UTF-8
 
 export CONTAINER_NAME=ci_native_qt5
-export CI_IMAGE_NAME_TAG=debian:buster
-# Use minimum supported python3.7 and gcc-8, see doc/dependencies.md
-export PACKAGES="gcc-8 g++-8 python3-zmq qtbase5-dev qttools5-dev-tools libdbus-1-dev libharfbuzz-dev"
-export DEP_OPTS="NO_QT=1 NO_UPNP=1 NO_NATPMP=1 DEBUG=1 ALLOW_HOST_PACKAGES=1 CC=gcc-8 CXX=g++-8"
+export CI_IMAGE_NAME_TAG="ubuntu:20.04"
+# Use minimum supported python3.8 and gcc-8 (or best-effort gcc-9), see doc/dependencies.md
+export PACKAGES="gcc-9 g++-9 python3-zmq qtbase5-dev qttools5-dev-tools libdbus-1-dev libharfbuzz-dev"
+export DEP_OPTS="NO_QT=1 NO_UPNP=1 NO_NATPMP=1 DEBUG=1 ALLOW_HOST_PACKAGES=1 CC=gcc-9 CXX=g++-9"
 export TEST_RUNNER_EXTRA="--previous-releases --coverage --extended --exclude feature_dbcrash"  # Run extended tests so that coverage does not fail, but exclude the very slow dbcrash
 export RUN_UNIT_TESTS_SEQUENTIAL="true"
 export RUN_UNIT_TESTS="false"
@@ -18,4 +18,4 @@ export GOAL="install"
 export NO_WERROR=1
 export DOWNLOAD_PREVIOUS_RELEASES="true"
 export BITCOIN_CONFIG="--enable-zmq --with-libs=no --with-gui=qt5 --enable-reduce-exports \
---enable-debug CFLAGS=\"-g0 -O2 -funsigned-char\" CXXFLAGS=\"-g0 -O2 -funsigned-char\" CC=gcc-8 CXX=g++-8"
+--enable-debug CFLAGS=\"-g0 -O2 -funsigned-char\" CXXFLAGS=\"-g0 -O2 -funsigned-char\""

configure.ac

@@ -126,8 +126,8 @@ AC_PATH_TOOL([AR], [ar])
 AC_PATH_TOOL([GCOV], [gcov])
 AC_PATH_TOOL([LLVM_COV], [llvm-cov])
 AC_PATH_PROG([LCOV], [lcov])
-dnl Python 3.7 is specified in .python-version and should be used if available, see doc/dependencies.md
-AC_PATH_PROGS([PYTHON], [python3.7 python3.8 python3.9 python3.10 python3.11 python3.12 python3 python])
+dnl Python 3.8 is specified in .python-version and should be used if available, see doc/dependencies.md
+AC_PATH_PROGS([PYTHON], [python3.8 python3.9 python3.10 python3.11 python3.12 python3 python])
 AC_PATH_PROG([GENHTML], [genhtml])
 AC_PATH_PROG([GIT], [git])
 AC_PATH_PROG([CCACHE], [ccache])

doc/dependencies.md

@@ -10,7 +10,7 @@ You can find installation instructions in the `build-*.md` file for your platfor
 | [Automake](https://www.gnu.org/software/automake/) | [1.13](https://github.com/bitcoin/bitcoin/pull/18290) |
 | [Clang](https://clang.llvm.org) | [8.0](https://github.com/bitcoin/bitcoin/pull/24164) |
 | [GCC](https://gcc.gnu.org) | [8.1](https://github.com/bitcoin/bitcoin/pull/23060) |
-| [Python](https://www.python.org) (tests) | [3.7](https://github.com/bitcoin/bitcoin/pull/26226) |
+| [Python](https://www.python.org) (scripts, tests) | [3.8](https://github.com/bitcoin/bitcoin/pull/27483) |
 | [systemtap](https://sourceware.org/systemtap/) ([tracing](tracing.md))| N/A |
 
 ## Required