Make Junit report success callout message conditional

Also add $GOPATH/bin to $PATH

scripts/test_lib.sh

@@ -230,19 +230,26 @@ function produce_junit_xmlreport {
 
   local junit_xml_filename
   junit_xml_filename="${junit_filename_prefix}.xml"
+  local PATH
 
   if ! command -v gotestsum >/dev/null 2>&1; then
     log_callout "gotestsum not found; installing now"
     pushd "${ETCD_ROOT_DIR}/tools/mod" >/dev/null || return
       GO111MODULE=on go install gotest.tools/gotestsum
     popd >/dev/null || return
+    export PATH=$(go env PATH):$(go env GOPATH)/bin
   fi
   gotestsum --junitfile "${junit_xml_filename}" --raw-command cat "${junit_filename_prefix}"*.stdout
+  local cmd_code=$?
   if [ "${VERBOSE}" != "1" ]; then
     rm "${junit_filename_prefix}"*.stdout
   fi
 
-  log_callout "Saved JUnit XML test report to ${junit_xml_filename}"
+  if [ ${cmd_code} -ne 0 ]; then
+    log_error "gotestsum failed and did not generate JUnit XML test report"
+  else
+    log_callout "Saved JUnit XML test report to ${junit_xml_filename}"
+  fi
 }