patch [#33669] SConstruct: Tell how to pass BF_PYTHON_INC to SCons is it is not found

from anatoly techtonik (techtonik)

SConstruct

@@ -442,11 +442,12 @@ if env['WITH_BF_PYTHON']:
             found_pyconfig_h = True
 
     if not (found_python_h and found_pyconfig_h):
-        print("\nMissing: Python.h and/or pyconfig.h in\"" + env.subst('${BF_PYTHON_INC}') + "\",\n"
-              "  Set 'BF_PYTHON_INC' to point "
-              "to valid python include path(s).\n Containing "
-              "Python.h and pyconfig.h for python version \"" + env.subst('${BF_PYTHON_VERSION}') + "\"")
+        print("""\nMissing: Python.h and/or pyconfig.h in "%s"
+         Set 'BF_PYTHON_INC' to point to valid include path(s),
+         containing Python.h and pyconfig.h for Python version "%s".
 
+         Example: python scons/scons.py BF_PYTHON_INC=../Python/include
+              """ % (env.subst('${BF_PYTHON_INC}'), env.subst('${BF_PYTHON_VERSION}')))
         Exit()