"kubectl exec" in Cygwin gets "Upgrade request required", but not in cmd shell

[David Karr <davidmichaelkarr@gmail.com>]

I've been using kubectl in Cygwin on Windows 10 for quite a while, to
communicate to our in-house k8s clusters. I often use "kubectl exec" to
open a shell in a container or directly execute a shell command.  This has
worked perfectly fine for a long time.

A couple of days ago, I discovered that all of these attempts were failing
with "Upgrade request required".  I hadn't upgraded kubectl or Cygwin in
quite a while. I doubt our clusters had a k8s upgrade, but it's entirely
possible.

A colleague of mine has a very similar desktop configuration (Windows 10,
Cygwin), and he's not seeing this symptom.

I noticed that when I ran "kubectl exec" with max verbosity, it shows the
resulting "curl" command that it runs. I tried that resulting command, and
it results in the same response. I then tried updating my Cygwin tools and
retesting, no change.

I then took the entire resulting "kubectl exec" command line and ran it in
a "cmd" shell.  No problem at all.  No error.

I know I haven't provided much useful information yet. I wanted to get an
initial response before I started providing those diagnostics. Is there a
clear issue here that I'm not aware of?