When we have pre-release version it is very unintuitive with the default error message, since just looking at the string
1.15.11-abs-1234 is larger than 1.15.11, but semver treats -abs-1234 as a prerelease version and hence smaller than
1.15.11.
So expand the error in this case
for #1883
* bump the minimum version to 1.15.1
Kubernetes 1.15.0 has a bug in openapi and conversion webhook does not
allow to deploy any Knative resources by kubectl.
To avoid hit the issue, this patch bumps the minimum version to
1.15.1.
Please refer to https://github.com/knative/serving/issues/6787 for
more detail.
* Fix unit test
Victor Agababov
Kenjiro Nakayama
Dave Protasowski
Markus Thömmes
Zhimin Xiang
Matt Moore