fix(python): read legacy TYPE_INT64 marshal values

Fixes #6609

src/python/PythonPycParser.ts

@@ -26,6 +26,7 @@ const TYPE_TRUE = 0x54;
 const TYPE_STOPITER = 0x53;
 const TYPE_ELLIPSIS = 0x2e;
 const TYPE_INT = 0x69;
+const TYPE_INT64 = 0x49;
 const TYPE_FLOAT_TEXT = 0x66;
 const TYPE_FLOAT = 0x67;
 const TYPE_COMPLEX_TEXT = 0x78;
@@ -390,6 +391,10 @@ class MarshalReader {
         const value = BigInt(this.i32());
         return { kind: "int", value, bits: smallBitLength(value) };
       }
+      case TYPE_INT64: {
+        const value = this.i64();
+        return { kind: "int", value, bits: smallBitLength(value) };
+      }
       case TYPE_FLOAT_TEXT:
         return { kind: "float", value: this.textFloat() };
       case TYPE_FLOAT:
@@ -1514,6 +1519,14 @@ class MarshalReader {
     return value;
   }
 
+  i64(): bigint {
+    if (this.offset > this.bytes.length - 8)
+      malformed("Marshal stream ended inside a 64-bit integer.");
+    const value = this.bytes.readBigInt64LE(this.offset);
+    this.offset += 8;
+    return value;
+  }
+
   /** CPython `r_long` count fields that its constructors require non-negative. */
   nonNegativeInt32(field: string): number {
     const value = this.i32();