configure: Add courtesy hint to Python version failure message

If we begin requiring Python 3.7+, a few platforms are going to need to
install an additional Python interpreter package.

As a courtesy to the user, suggest the optional package they might need
to install. This will hopefully minimize any downtime caused by the
change in Python dependency.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230221012456.2607692-3-jsnow@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20230511035435.734312-25-jsnow@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

configure

@@ -1091,7 +1091,10 @@ fi
 
 if ! check_py_version "$python"; then
   error_exit "Cannot use '$python', Python >= 3.7 is required." \
-      "Use --python=/path/to/python to specify a supported Python."
+             "Use --python=/path/to/python to specify a supported Python." \
+             "Maybe try:" \
+             "  openSUSE Leap 15.3+: zypper install python39" \
+             "  CentOS 8: dnf install python38"
 fi
 
 # Resolve PATH