Issue #3137: Don't ignore errors at startup, especially a keyboard interrupt

(SIGINT). If an error occurs while importing the site module, the error is
printed and Python exits. Initialize the GIL before importing the site
module.

Lib/site.py

@@ -489,6 +489,12 @@ def execsitecustomize():
         import sitecustomize
     except ImportError:
         pass
+    except Exception:
+        if sys.flags.verbose:
+            sys.excepthook(*sys.exc_info())
+        else:
+            print >>sys.stderr, \
+                "'import sitecustomize' failed; use -v for traceback"
 
 
 def execusercustomize():
@@ -497,6 +503,12 @@ def execusercustomize():
         import usercustomize
     except ImportError:
         pass
+    except Exception:
+        if sys.flags.verbose:
+            sys.excepthook(*sys.exc_info())
+        else:
+            print>>sys.stderr, \
+                "'import sitecustomize' failed; use -v for traceback"
 
 
 def main():

Misc/NEWS

@@ -12,6 +12,11 @@ What's New in Python 2.7 beta 1?
 Core and Builtins
 -----------------
 
+- Issue #3137: Don't ignore errors at startup, especially a keyboard interrupt
+  (SIGINT). If an error occurs while importing the site module, the error is
+  printed and Python exits. Initialize the GIL before importing the site
+  module.
+
 Library
 -------
 

Modules/main.c

@@ -573,10 +573,16 @@ Py_Main(int argc, char **argv)
 		}
 
 		if (sts==-1) {
-			sts = PyRun_AnyFileExFlags(
-				fp,
-				filename == NULL ? "<stdin>" : filename,
-				filename != NULL, &cf) != 0;
+			/* call pending calls like signal handlers (SIGINT) */
+			if (Py_MakePendingCalls() == -1) {
+				PyErr_Print();
+				sts = 1;
+			} else {
+				sts = PyRun_AnyFileExFlags(
+					fp,
+					filename == NULL ? "<stdin>" : filename,
+					filename != NULL, &cf) != 0;
+			}
 		}
 		
 	}

Parser/tokenizer.c

@@ -817,8 +817,12 @@ error_nomem:
 	return -1;
 
 error_clear:
-	/* Fallback to iso-8859-1: for backward compatibility */
 	Py_DECREF(enc);
+	if (!PyErr_ExceptionMatches(PyExc_UnicodeDecodeError)) {
+		tok->done = E_ERROR;
+		return -1;
+	}
+	/* Fallback to iso-8859-1: for backward compatibility */
 	PyErr_Clear();
 	return 0;
 }

Python/import.c

@@ -2748,8 +2748,6 @@ PyImport_Import(PyObject *module_name)
 	}
 	else {
 		/* No globals -- use standard builtins, and fake globals */
-		PyErr_Clear();
-
 		builtins = PyImport_ImportModuleLevel("__builtin__",
 						      NULL, NULL, NULL, 0);
 		if (builtins == NULL)

Python/pythonrun.c

@@ -248,14 +248,15 @@ Py_InitializeEx(int install_sigs)
 	}
 
 	initmain(); /* Module __main__ */
-	if (!Py_NoSiteFlag)
-		initsite(); /* Module site */
 
 	/* auto-thread-state API, if available */
 #ifdef WITH_THREAD
 	_PyGILState_Init(interp, tstate);
 #endif /* WITH_THREAD */
 
+	if (!Py_NoSiteFlag)
+		initsite(); /* Module site */
+
 	if ((p = Py_GETENV("PYTHONIOENCODING")) && *p != '\0') {
 		p = icodeset = codeset = strdup(p);
 		free_codeset = 1;
@@ -284,8 +285,13 @@ Py_InitializeEx(int install_sigs)
 				loc_codeset = strdup(loc_codeset);
 				Py_DECREF(enc);
 			} else {
-				loc_codeset = NULL;
-				PyErr_Clear();
+				if (PyErr_ExceptionMatches(PyExc_LookupError)) {
+					PyErr_Clear();
+					loc_codeset = NULL;
+				} else {
+					PyErr_Print();
+					exit(1);
+				}
 			}
 		} else
 			loc_codeset = NULL;
@@ -704,20 +710,12 @@ initmain(void)
 static void
 initsite(void)
 {
-	PyObject *m, *f;
+	PyObject *m;
 	m = PyImport_ImportModule("site");
 	if (m == NULL) {
-		f = PySys_GetObject("stderr");
-		if (Py_VerboseFlag) {
-			PyFile_WriteString(
-				"'import site' failed; traceback:\n", f);
-			PyErr_Print();
-		}
-		else {
-			PyFile_WriteString(
-			  "'import site' failed; use -v for traceback\n", f);
-			PyErr_Clear();
-		}
+		PyErr_Print();
+		Py_Finalize();
+		exit(1);
 	}
 	else {
 		Py_DECREF(m);
@@ -1546,6 +1544,8 @@ err_input(perrdetail *err)
 	char *msg = NULL;
 	errtype = PyExc_SyntaxError;
 	switch (err->error) {
+	case E_ERROR:
+		return;
 	case E_SYNTAX:
 		errtype = PyExc_IndentationError;
 		if (err->expected == INDENT)