Fix py3k

Enable syntax errors to properly surface invalid code in py3
porting mode, instead of silently swallowing them and giving
the incorrect impression that the code is valid for py3.

Closes #2956

Author: hugues-aff

CONTRIBUTORS.txt

@@ -340,3 +340,6 @@ contributors:
 * laike9m: contributor
 
 * Janne Rönkkö: contributor
+
+* Hugues Bruant: contributor
+

ChangeLog

@@ -33,6 +33,10 @@ Release date: TBA
 
 * Allow parallel linting when run under Prospector
 
+* Python 3 porting mode no longer swallows syntax errors
+
+  Closes #2956
+
 
 What's New in Pylint 2.4.3?
 ===========================

pylint/lint.py

@@ -748,6 +748,11 @@ def error_mode(self):
     def python3_porting_mode(self):
         """Disable all other checkers and enable Python 3 warnings."""
         self.disable("all")
+        # re-enable some errors, or 'print', 'raise', 'async', 'await' will mistakenly lint fine
+        self.enable("F0001")
+        self.enable("F0002")
+        self.enable("F0010")
+        self.enable("E0001")
         self.enable("python3")
         if self._error_mode:
             # The error mode was activated, using the -E flag.