git push via VC failure

[Stephen Berman]

I've recently pushed a few commits to emacs-26 and master, and in each
case, tying 'P' in the *vc-dir* buffer failed; but typing 'git push' in
bash succeeded.  Here is the output displayed in the vc-git compilation
buffer:

txtxJRZ3BKKHm.txt
Description: vc-git compilation output

I've gotten this on two different GNU/Linux systems, one does not have
ssh-askpass installed, the other does but it is in /usr/libexec/openssh;
so does VC really require ssh-askpass directly in /usr/libexec?  If so,
I guess I could symlink it there, but this seems suboptimal.  Again, in
both systems 'git push' from the shell succeeded, so git itself seems to
be configured correctly and ssh-askpass doesn't seem to be required.  Or
is there some other reason for the failure in VC?

Steve Berman