Bug#1140587: python3-casadi should not use dpkg-architecture in postinst

[Helmut Grohne]

Package: python3-casadi
Version: 3.7.0+ds2-3
Severity: important

Installing python3-casadi gives me:

| /var/lib/dpkg/info/python3-casadi.postinst: 8: dpkg-architecture: not found

Looking into its postinst reveals that it uses dpkg-architecture for
computing a path in the package at runtime. The result of this will be
wrong for foreign installation. It is not sufficient here to add a
dependency on dpkg-dev.

Instead, please compute the path at build time. Note that dh_installdeb
will substitute #DEB_HOST_MULTIARCH#.

Helmut