hplip messed up python versions (2/3) in disco

[Sergio Callegari]

Hplip installs cupsext for python3, but then hp-doctor is configured as a python (aka python2) script and fails.

Editing the shebang of hp-doctor to #!/usr/bin/python3 seems to fix the issue

ProblemType: Bug
DistroRelease: Ubuntu 19.04
Package: hplip 3.19.1+dfsg0-1
ProcVersionSignature: Ubuntu 5.0.0-20.21-generic 5.0.8
Uname: Linux 5.0.0-20-generic x86_64
ApportVersion: 2.20.10-0ubuntu27
Architecture: amd64
CurrentDesktop: KDE
Date: Fri Jul 5 09:04:59 2019
EcryptfsInUse: Yes
InstallationDate: Installed on 2013-12-12 (2030 days ago)
InstallationMedia: Kubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
MachineType: Notebook W740SU
Papersize: a4
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.0.0-20-generic root=/dev/mapper/zagar_ssd--vg-root ro quiet splash resume=/dev/zagar_ssd-vg/swap_1 acpi_backlight=vendor
SourcePackage: hplip
UpgradeStatus: Upgraded to disco on 2019-06-12 (22 days ago)
dmi.bios.date: 10/02/2013
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 4.6.5
dmi.board.asset.tag: Tag 12345
dmi.board.name: W740SU
dmi.board.vendor: Notebook
dmi.board.version: Not Applicable
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 9
dmi.chassis.vendor: Notebook
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr4.6.5:bd10/02/2013:svnNotebook:pnW740SU:pvrNotApplicable:rvnNotebook:rnW740SU:rvrNotApplicable:cvnNotebook:ct9:cvrN/A:
dmi.product.family: Not Applicable
dmi.product.name: W740SU
dmi.product.sku: Not Applicable
dmi.product.version: Not Applicable
dmi.sys.vendor: Notebook