compiler: improve error for import of non-string

Change-Id: I97fc28fc21166e024cb5906da894075f8315669b
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/273867
Trust: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
diff --git a/go/parse.cc b/go/parse.cc
index aa157e8..1dac002 100644
--- a/go/parse.cc
+++ b/go/parse.cc
@@ -5788,7 +5788,7 @@
 
   if (!token->is_string())
     {
-      go_error_at(this->location(), "import statement not a string");
+      go_error_at(this->location(), "import path must be a string");
       this->advance_token();
       return;
     }