Add assertion for PythonLanguage.MINOR_VERSION <= 10 to CSVModuleBuiltins.

Also update comments about compatability with CPython for clarity.

Author: phoeinx

graalpython/com.oracle.graal.python.test/src/tests/test_csv.py

@@ -75,7 +75,7 @@ def test_write_utf32_field_with_utf32_delimiter(self):
                              expected + writer.dialect.lineterminator)
 
 class TestDialectValidity(unittest.TestCase):
-    # CPython supports empty quotechars and escapechars until 3.10.
+    # CPython supports empty quotechars and escapechars until inclusive 3.10.
     def test_quoting(self):
         class MyDialect(csv.Dialect):
             delimiter = ";"

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/csv/CSVModuleBuiltins.java

@@ -48,6 +48,7 @@
 
 import java.util.List;
 
+import com.oracle.graal.python.PythonLanguage;
 import com.oracle.graal.python.builtins.Builtin;
 import com.oracle.graal.python.builtins.CoreFunctions;
 import com.oracle.graal.python.builtins.Python3Core;
@@ -93,6 +94,11 @@
 @CoreFunctions(defineModule = "_csv")
 public final class CSVModuleBuiltins extends PythonBuiltins {
 
+    static {
+        // See comment about Python 3.10 in #getChar() and graalpython/test/test_csv.py
+        assert PythonLanguage.MINOR <= 10;
+    }
+
     static final String WRITE = "write";
     static final String NOT_SET = "NOT_SET";
     static final int NOT_SET_CODEPOINT = -1;
@@ -535,7 +541,7 @@ private String getChar(String name, Object valueObj, String defaultValue,
                 throw raise(TypeError, ErrorMessages.MUST_BE_ONE_CHARACTER_STRING, name);
             }
 
-            // CPython supports empty quotechars and escapechars until 3.10.
+            // CPython supports empty quotechars and escapechars until inclusive 3.10.
             if (charValue.length() == 0) {
                 return NOT_SET;
             }