wxPython4 sequels: fix exception in connection dialog, force black text in FBD.
- wxPython4 does not have RemoveSizer in API anymore.
- On GTK3 with dark theme default text colour is white, making it unreadable.
<xsd:element name="Xenomai">
<xsd:complexType>
%(toolchain_gcc)s
<xsd:attribute name="XenoConfig" type="xsd:string" use="optional" default="xeno-config"/>
</xsd:complexType>
</xsd:element>