Only raise first exception and remove test case

src/black/parsing.py

@@ -108,34 +108,29 @@ def lib2to3_unparse(node: Node) -> str:
 
 def parse_ast(src: str) -> Union[ast.AST, ast3.AST, ast27.AST]:
     filename = "<unknown>"
-    error = None
+    first_error = ""
     if sys.version_info >= (3, 8):
         # TODO: support Python 4+ ;)
         for minor_version in range(sys.version_info[1], 4, -1):
             try:
                 return ast.parse(src, filename, feature_version=(3, minor_version))
             except SyntaxError as e:
-                if error is None:
-                    error = str(e)
-                continue
+                if not first_error:
+                    first_error = str(e)
     else:
         for feature_version in (7, 6):
             try:
                 return ast3.parse(src, filename, feature_version=feature_version)
-            except SyntaxError as e:
-                if error is None:
-                    error = str(e)
-                continue
-    if ast27.__name__ == "ast":
-        raise SyntaxError(
-            "The requested source code has invalid Python 3 syntax.\n"
-            "If you are trying to format Python 2 files please reinstall Black"
-            " with the 'python2' extra: `python3 -m pip install black[python2]`."
-        )
-    try:
-        return ast27.parse(src)
-    except SyntaxError as e:
-        raise SyntaxError(error or str(e))
+            except SyntaxError:
+                pass
+
+    if ast27.__name__ != "ast":
+        try:
+            return ast27.parse(src)
+        except SyntaxError:
+            pass
+
+    raise SyntaxError(first_error)
 
 
 def stringify_ast(

tests/test_black.py

@@ -448,60 +448,6 @@ def test_skip_magic_trailing_comma(self) -> None:
             )
             self.assertEqual(expected, actual, msg)
 
-    @pytest.mark.no_python2
-    def test_python2_should_fail_without_optional_install(self) -> None:
-        if sys.version_info < (3, 8):
-            self.skipTest(
-                "Python 3.6 and 3.7 will install typed-ast to work and as such will be"
-                " able to parse Python 2 syntax without explicitly specifying the"
-                " python2 extra"
-            )
-
-        source = "x = 1234l"
-        tmp_file = Path(black.dump_to_file(source))
-        try:
-            runner = BlackRunner()
-            result = runner.invoke(black.main, [str(tmp_file)])
-            self.assertEqual(result.exit_code, 123)
-        finally:
-            os.unlink(tmp_file)
-        actual = (
-            result.stderr_bytes.decode()
-            .replace("\n", "")
-            .replace("\\n", "")
-            .replace("\\r", "")
-            .replace("\r", "")
-        )
-        msg = (
-            "The requested source code has invalid Python 3 syntax."
-            "If you are trying to format Python 2 files please reinstall Black"
-            " with the 'python2' extra: `python3 -m pip install black[python2]`."
-        )
-        self.assertIn(msg, actual)
-
-    @pytest.mark.python2
-    def test_safety_check_syntax_error(self) -> None:
-        source = "e = 'test'\nx = f'{'"
-        tmp_file = Path(black.dump_to_file(source))
-        try:
-            runner = BlackRunner()
-            result = runner.invoke(black.main, [str(tmp_file)])
-            self.assertEqual(result.exit_code, 123)
-        finally:
-            os.unlink(tmp_file)
-        actual = (
-            runner.stderr_bytes.decode()
-            .replace("\n", "")
-            .replace("\\n", "")
-            .replace("\\r", "")
-            .replace("\r", "")
-        )
-        msg = (
-            "cannot use --safe with this file; failed to parse source file."
-            "  AST error message: f-string: expecting '}' (<unknown>, line 2)"
-        )
-        self.assertIn(msg, actual)
-
     @pytest.mark.python2
     @patch("black.dump_to_file", dump_to_stderr)
     def test_python2_print_function(self) -> None: