Parser: Add Python 3 keywords.

RELNOTES: Python 3 keywords are added to the lexer. They cannot be used as identifiers.

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MOS_MIGRATED_REVID=89301541

src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java

diff --git a/src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java b/src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java
index 07501da..afca4b3 100644
--- a/src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java
+++ b/src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java
@@ -313,6 +313,14 @@
   }
 
   @Test
+  public void testAssignKeyword() {
+    syntaxEvents.setFailFast(false);
+    parseExpr("with = 4");
+    syntaxEvents.assertContainsEvent("syntax error at 'with': expected expression");
+    syntaxEvents.collector().clear();
+  }
+
+  @Test
   public void testTupleAssign() {
     String expr = "list[0] = 5; dict['key'] = value\n";
     List<Statement> statements = parseFile(expr);