fix problem running PLCOpenEditor

$ ./PLCOpenEditor.py
../src/common/stdpbase.cpp(62): assert "traits" failed in Get(): create wxApp before calling this

Regression was introduced by '3311eea' (clean-up: fix PEP8 E402 module level import not at top of file)

                  <xsd:element name="Generic">
                    <xsd:complexType>
                      %(toolchain_makefile)s
                    </xsd:complexType>
                  </xsd:element>