Always report fatal errors.

Previously these could be suppressed if error holding was in place.

This was noticed in #1746.

Cython/Compiler/Errors.py

@@ -145,8 +145,8 @@ def close_listing_file():
         listing_file.close()
         listing_file = None
 
-def report_error(err):
-    if error_stack:
+def report_error(err, use_stack=True):
+    if error_stack and use_stack:
         error_stack[-1].append(err)
     else:
         global num_errors

Cython/Compiler/Pipeline.py

@@ -343,7 +343,7 @@ def run_pipeline(pipeline, source, printtree=True):
                         print("    %.3f seconds" % (time() - t))
         except CompileError as err:
             # err is set
-            Errors.report_error(err)
+            Errors.report_error(err, use_stack=False)
             error = err
     except InternalError as err:
         # Only raise if there was not an earlier error