`go get -u` panic

00-repro-steps.txt

$ go version
go version go1.6.1 linux/amd64
$ rm -rf src/github.com/qmsk/e2/
$ GOPATH=~/go go get -v -u github.com/qmsk/e2/cmd/tally
github.com/qmsk/e2 (download)
github.com/jessevdk/go-flags (download)
github.com/golang/glog (download)
github.com/qmsk/e2/discovery
github.com/qmsk/e2/vendor/github.com/kidoman/embd
github.com/qmsk/e2/client
github.com/qmsk/e2/vendor/github.com/kidoman/embd/host/generic
github.com/qmsk/e2/vendor/github.com/kidoman/embd/host/rpi
github.com/qmsk/e2/tally
github.com/qmsk/e2/cmd/tally
$ rm -rf src/github.com/qmsk/e2/vendor/github.com/kidoman/embd/
$ GOPATH=~/go go get -v -u github.com/qmsk/e2/cmd/tally
github.com/qmsk/e2 (download)
github.com/jessevdk/go-flags (download)
github.com/kidoman/embd (download)
github.com/golang/glog (download)
panic: runtime error: slice bounds out of range

goroutine 1 [running]:
panic(0x93d000, 0xc820010090)
        /usr/lib/go-1.6/src/runtime/panic.go:464 +0x3e6
main.vendoredImportPath(0xc8203ee800, 0xc820459c21, 0x24, 0x0, 0x0)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:460 +0x67b
main.loadImport(0xc820459c21, 0x24, 0xc820205e00, 0x50, 0xc8203ee800, 0xc8205557e8, 0xc820459d10, 0x1, 0x1, 0x1, ...)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:336 +0xe52
main.(*Package).load(0xc8203ee800, 0xc8205557e8, 0xc820296700, 0x0, 0x0, 0x4)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:947 +0x4397
main.loadImport(0xc82029f0b1, 0x20, 0xc82029eae0, 0x2e, 0xc820336400, 0xc8205557e8, 0xc82029f3b0, 0x1, 0x1, 0x1, ...)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:377 +0x84e
main.(*Package).load(0xc820336400, 0xc8205557e8, 0xc8201eee00, 0x0, 0x0, 0x4)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:947 +0x4397
main.loadImport(0xc8200ca241, 0x18, 0xc820171740, 0x32, 0xc8203efc00, 0xc8205557e8, 0xc8203ea900, 0x1, 0x1, 0x1, ...)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:377 +0x84e
main.(*Package).load(0xc8203efc00, 0xc8205557e8, 0xc82028b880, 0x0, 0x0, 0xc)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:947 +0x4397
main.loadImport(0x7ffda4674811, 0x1c, 0xc82000e0c4, 0x11, 0x0, 0xc8205557e8, 0x0, 0x0, 0x0, 0x0, ...)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:377 +0x84e
main.loadPackage(0x7ffda4674811, 0x1c, 0xc8205557e8, 0x0)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:1633 +0x13d8
main.packagesAndErrors(0xc8201ac430, 0x1, 0x1, 0x0, 0x0, 0x0)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:1678 +0x531
main.packagesForBuild(0xc8201ac400, 0x1, 0x1, 0x0, 0x0, 0x0)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:1694 +0x82
main.runGet(0xc891a0, 0xc8201ac400, 0x1, 0x1)
        /usr/lib/go-1.6/src/cmd/go/get.go:123 +0x322
main.main()
        /usr/lib/go-1.6/src/cmd/go/main.go:181 +0x783

10-orig-scenario.txt

$ go version
go version go1.6.1 linux/amd64

$ GOPATH=~/go go get -v github.com/qmsk/e2/cmd/tally
github.com/qmsk/e2 (download)
# cd /home/tjmartti/go/src/github.com/qmsk/e2; git submodule update --init --recursive
Submodule 'vendor/github.com/kidoman/embd' (git@github.com:SpComb/embd.git) registered for path 'vendor/github.com/kidoman/embd'
Cloning into 'vendor/github.com/kidoman/embd'...
Warning: Permanently added the RSA host key for IP address '192.30.252.120' to the list of known hosts.
Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
fatal: clone of 'git@github.com:SpComb/embd.git' into submodule path 'vendor/github.com/kidoman/embd' failed
package github.com/qmsk/e2/cmd/tally: exit status 128
$ logout

# try again with the correct SSH keys available
$ GOPATH=~/go go get -v -u github.com/qmsk/e2/cmd/tally
github.com/qmsk/e2 (download)
github.com/jessevdk/go-flags (download)
github.com/kidoman/embd (download)
github.com/golang/glog (download)
panic: runtime error: slice bounds out of range

goroutine 1 [running]:
panic(0x93d000, 0xc820010090)
        /usr/lib/go-1.6/src/runtime/panic.go:464 +0x3e6
main.vendoredImportPath(0xc8203e6400, 0xc820295e01, 0x24, 0x0, 0x0)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:460 +0x67b
main.loadImport(0xc820295e01, 0x24, 0xc82024b4a0, 0x50, 0xc8203e6400, 0xc8205437e8, 0xc820295f50, 0x1, 0x1, 0x1, ...)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:336 +0xe52
main.(*Package).load(0xc8203e6400, 0xc8205437e8, 0xc820314700, 0x0, 0x0, 0x4)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:947 +0x4397
main.loadImport(0xc82027c5a1, 0x20, 0xc82027c240, 0x2e, 0xc820471c00, 0xc8205437e8, 0xc82027c6f0, 0x1, 0x1, 0x1, ...)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:377 +0x84e
main.(*Package).load(0xc820471c00, 0xc8205437e8, 0xc820123c00, 0x0, 0x0, 0x4)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:947 +0x4397
main.loadImport(0xc820316241, 0x18, 0xc8201b4000, 0x32, 0xc82040dc00, 0xc8205437e8, 0xc8202d69c0, 0x1, 0x1, 0x1, ...)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:377 +0x84e
main.(*Package).load(0xc82040dc00, 0xc8205437e8, 0xc8201e0000, 0x0, 0x0, 0xc)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:947 +0x4397
main.loadImport(0x7ffd0a6ad811, 0x1c, 0xc82000e0c4, 0x11, 0x0, 0xc8205437e8, 0x0, 0x0, 0x0, 0x0, ...)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:377 +0x84e
main.loadPackage(0x7ffd0a6ad811, 0x1c, 0xc8205437e8, 0x0)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:1633 +0x13d8
main.packagesAndErrors(0xc820229f90, 0x1, 0x1, 0x0, 0x0, 0x0)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:1678 +0x531
main.packagesForBuild(0xc820229f40, 0x1, 0x1, 0x0, 0x0, 0x0)
        /usr/lib/go-1.6/src/cmd/go/pkg.go:1694 +0x82
main.runGet(0xc891a0, 0xc820229f40, 0x1, 0x1)
        /usr/lib/go-1.6/src/cmd/go/get.go:123 +0x322
main.main()
        /usr/lib/go-1.6/src/cmd/go/main.go:181 +0x783