Seems to be happening enough to warrant a bug:

https://search.ci.openshift.org/?search=error+reading+Main+Route+Table+Association.*empty+result&maxAge=168h&context=1&type=bug%2Bissue%2Bjunit&name=&excludeName=&maxMatches=5&maxBytes=20971520&groupBy=job

Example: https://prow.ci.openshift.org/view/gs/origin-ci-test/logs/periodic-ci-openshift-release-master-nightly-4.13-e2e-aws-sdn-serial/1595035189786972160

level=error msg=Error: error reading Main Route Table Association (rtbassoc-079775c2f52edb8c8): empty result
level=error
level=error msg= with module.vpc.aws_main_route_table_association.main_vpc_routes[0],
level=error msg= on vpc/vpc-public.tf line 27, in resource "aws_main_route_table_association" "main_vpc_routes":
level=error msg= 27: resource "aws_main_route_table_association" "main_vpc_routes" {
level=error
level=error msg=failed to fetch Cluster: failed to generate asset "Cluster": failure applying terraform for "cluster" stage: failed to create cluster: failed to apply Terraform: exit status 1
level=error
level=error msg=Error: error reading Main Route Table Association (rtbassoc-079775c2f52edb8c8): empty result
level=error
level=error msg= with module.vpc.aws_main_route_table_association.main_vpc_routes[0],
level=error msg= on vpc/vpc-public.tf line 27, in resource "aws_main_route_table_association" "main_vpc_routes":
level=error msg= 27: resource "aws_main_route_table_association" "main_vpc_routes" {