Handle error when creating etcd client

lib/backend/etcdv3/etcdv3.go

@@ -60,7 +60,11 @@ func NewEtcdV3Client(config *apiconfig.EtcdConfig) (api.Client, error) {
 		CertFile: config.EtcdCertFile,
 		KeyFile:  config.EtcdKeyFile,
 	}
-	tls, _ := tlsInfo.ClientConfig()
+
+	tls, err := tlsInfo.ClientConfig()
+	if err != nil {
+		return nil, fmt.Errorf("could not initialize etcdv3 client: %+v", err)
+	}
 
 	// Build the etcdv3 config.
 	cfg := clientv3.Config{

lib/backend/etcdv3/etcdv3_test.go

@@ -0,0 +1,32 @@
+package etcdv3_test
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+	"github.com/projectcalico/libcalico-go/lib/apiconfig"
+	"github.com/projectcalico/libcalico-go/lib/backend/etcdv3"
+)
+
+var _ = Describe("RulesAPIToBackend", func() {
+	It("should raise an error if specified certs don't exist", func() {
+		_, err := etcdv3.NewEtcdV3Client(&apiconfig.EtcdConfig{
+			EtcdCACertFile: "/fake/path",
+			EtcdCertFile:   "/fake/path",
+			EtcdKeyFile:    "/fake/path",
+			EtcdEndpoints:  "http://fake:2379",
+		})
+
+		Expect(err).To(HaveOccurred())
+	})
+
+	It("shouldn't create a client with empty certs", func() {
+		_, err := etcdv3.NewEtcdV3Client(&apiconfig.EtcdConfig{
+			EtcdCACertFile: "/dev/null",
+			EtcdCertFile:   "/dev/null",
+			EtcdKeyFile:    "/dev/null",
+			EtcdEndpoints:  "http://fake:2379",
+		})
+
+		Expect(err).To(HaveOccurred())
+	})
+})