Revert "Drop support for Python 3.8"

This reverts commit 3d5b2f81fb.

It should not be in 10.0.x branch, since we do support python 3.8
in 10.0.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

configure

@@ -540,17 +540,17 @@ if test -n "$linux_arch" && ! test -d "$source_path/linux-headers/asm-$linux_arc
 fi
 
 check_py_version() {
-    # We require python >= 3.9.
+    # We require python >= 3.8.
     # NB: a True python conditional creates a non-zero return code (Failure)
-    "$1" -c 'import sys; sys.exit(sys.version_info < (3,9))'
+    "$1" -c 'import sys; sys.exit(sys.version_info < (3,8))'
 }
 
 first_python=
 if test -z "${PYTHON}"; then
     # A bare 'python' is traditionally python 2.x, but some distros
     # have it as python 3.x, so check in both places.
-    for binary in python3 python python3.13 python3.12 python3.11 \
-                          python3.10 python3.9 ; do
+    for binary in python3 python python3.12 python3.11 \
+                          python3.10 python3.9 python3.8; do
         if has "$binary"; then
             python=$(command -v "$binary")
             if check_py_version "$python"; then
@@ -933,7 +933,7 @@ then
     # If first_python is set, there was a binary somewhere even though
     # it was not suitable.  Use it for the error message.
     if test -n "$first_python"; then
-        error_exit "Cannot use '$first_python', Python >= 3.9 is required." \
+        error_exit "Cannot use '$first_python', Python >= 3.8 is required." \
             "Use --python=/path/to/python to specify a supported Python."
     else
         error_exit "Python not found. Use --python=/path/to/python"
@@ -941,11 +941,11 @@ then
 fi
 
 if ! check_py_version "$python"; then
-  error_exit "Cannot use '$python', Python >= 3.9 is required." \
+  error_exit "Cannot use '$python', Python >= 3.8 is required." \
              "Use --python=/path/to/python to specify a supported Python." \
              "Maybe try:" \
              "  openSUSE Leap 15.3+: zypper install python39" \
-             "  CentOS: dnf install python3.12"
+             "  CentOS 8: dnf install python38"
 fi
 
 # Resolve PATH