package-install-from-buffer moves point

[Peter Eisentraut]

package-install-from-buffer moves the point to somewhere in the package
header, because it moves around there as it parses the header entries.
This is pretty annoying when developing and testing a package.

This could be fixed by wrapping the body of package-buffer-info into
save-excursion.  This worked well for me, but it somehow broke several
tests in package-test.el in ways that I don't understand.  E.g.,

Test package-test-describe-package condition:
    (wrong-type-argument number-or-marker-p "Trace/BPT trap: 5")
   FAILED   4/19  package-test-describe-package

Any ideas?