Upstream version must start with digit

[loosebazooka]

If this is still being maintained, I think a check needs to be added to handle:

The upstream_version must contain only alphanumerics 6 and the characters . + - ~ (full stop, plus, hyphen, tilde) and should start with a digit

[n-oden]

https://github.com/memory/python-dpkg is the authoritative source these days, can you repost this there so I don't forget to check it?