The error message in this run should probably be a lot clearer, but it's
wasted time to replicate that work for VPM, as DUB already gives a
proper error message:

vela3:vibe.d sin$ vibe run --verbose examples/diet/
Notice: This VPM build script is deprecated. It is recommended to
use DUB instead.
See https://github.com/rejectedsoftware/dub

[0E869E01:00000000 dia] libevent version: 2.0.21-stable
[0E869E01:00000000 dia] libevent is using kqueue for events.
[0E869E01:00000000 dbg] Using vpm registry url 'http://registry.vibed.org/'
[0E869E01:00000000 dbg] Could not open vpm.json: Failed to open file '/Users/sin/Projekte/vibe.d/vpm.json'.
[0E869E01:00000000 dbg] opened file /Users/sin/Projekte/vibe.d/package.json with 1683 bytes as 7
Checking dependencies in '/Users/sin/Projekte/vibe.d'
[0E869E01:00000000 dbg] vpm initialized
[0E869E01:00000000 dbg] Application Name is 'app'
[0E869E01:00000000 dbg] opened file /var/folders/33/d0whv8kn1gb926ng6v6tvsr0000gn/T/vpm.start.XXXXXXXX.91KdmYLS with 0 bytes as 7
Error: cannot read file source/app.d
Failed: 'dmd' '-debug' '-g' '-w' '-property' '-g' '-I/Users/sin/Projekte/vibe.d/source' '-I/Users/sin/Projekte/vibe.d/import' '-Isource' '-Jviews' '-Isource' '-Jviews' '-Iimport' '-Isource' '-L-L/opt/local/lib' '-L-levent
pthreads' '-L-levent' '-L-L/opt/local/lib' '-L-lssl' '-L-lcrypto' '-version=VibeLibeventDriver' '-v' '-o-' 'source/app.d' '-Isource'

It should say something like "There was no source/app.d file found,
please run vibe from the root of a package directory".

Glad to see that at least it finally works again now.