configure: Python tests must be done before help message

The help message uses $python and displays its value, so that macro
should be tested and set early.

With this modification, configure --help displays the correct value
(usually python -B) and no longer creates several *.pyc files.
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

configure

@@ -1004,6 +1004,25 @@ for opt do
   esac
 done
 
+if ! has $python; then
+  error_exit "Python not found. Use --python=/path/to/python"
+fi
+
+# Note that if the Python conditional here evaluates True we will exit
+# with status 1 which is a shell 'false' value.
+if ! $python -c 'import sys; sys.exit(sys.version_info < (2,4) or sys.version_info >= (3,))'; then
+  error_exit "Cannot use '$python', Python 2.4 or later is required." \
+      "Note that Python 3 or later is not yet supported." \
+      "Use --python=/path/to/python to specify a supported Python."
+fi
+
+# The -B switch was added in Python 2.6.
+# If it is supplied, compiled files are not written.
+# Use it for Python versions which support it.
+if $python -B -c 'import sys; sys.exit(0)' 2>/dev/null; then
+  python="$python -B"
+fi
+
 case "$cpu" in
     ppc)
            CPU_CFLAGS="-m32"
@@ -1419,25 +1438,6 @@ if test "$solaris" = "yes" ; then
   fi
 fi
 
-if ! has $python; then
-  error_exit "Python not found. Use --python=/path/to/python"
-fi
-
-# Note that if the Python conditional here evaluates True we will exit
-# with status 1 which is a shell 'false' value.
-if ! $python -c 'import sys; sys.exit(sys.version_info < (2,4) or sys.version_info >= (3,))'; then
-  error_exit "Cannot use '$python', Python 2.4 or later is required." \
-      "Note that Python 3 or later is not yet supported." \
-      "Use --python=/path/to/python to specify a supported Python."
-fi
-
-# The -B switch was added in Python 2.6.
-# If it is supplied, compiled files are not written.
-# Use it for Python versions which support it.
-if $python -B -c 'import sys; sys.exit(0)' 2>/dev/null; then
-  python="$python -B"
-fi
-
 if test -z "${target_list+xxx}" ; then
     target_list="$default_target_list"
 else