Handle insufficient temp space better

[alert-debug]

If trying to create a .deb package on a system which has insufficient temp space, the stacktrace produced contains messages like:

org.vafer.jdeb.PackagingException: Could not create deb package
java.io.IOException: This archives contains unclosed entries.

but nothing which highlights the underlying issue. This leads to confusion which presumably explains tickets like this.

Having a separate check in createSignedDeb to catch the IOException and suggest a disk space problem (the most likely cause?) to the user would potentially speed up debugging this issue when people encounter it.

[tcurdt]

Fair point.