Actually retry every database error, including "pq: ..."

They aren't of type *pq.Error, but they're clearly database errors.

retry/retry.go

@@ -9,6 +9,7 @@ import (
 	"github.com/pkg/errors"
 	"io"
 	"net"
+	"strings"
 	"syscall"
 	"time"
 )
@@ -197,5 +198,11 @@ func Retryable(err error) bool {
 		return true
 	}
 
+	// For errors without a five-digit code, github.com/lib/pq uses fmt.Errorf().
+	// That returns an unexported error type, so we can only check the error message:
+	if strings.HasPrefix(err.Error(), "pq: ") {
+		return true
+	}
+
 	return false
 }