fixed segfault regression

news/sig.rst

@@ -0,0 +1,14 @@
+**Added:** None
+
+**Changed:** None
+
+**Deprecated:** None
+
+**Removed:** None
+
+**Fixed:**
+
+* Segfaults and other early exit signals are now reported correctly,
+  again.
+
+**Security:** None

xonsh/proc.py

@@ -872,6 +872,16 @@ class PopenThread(threading.Thread):
         """Process return code."""
         return self.proc.returncode
 
+    @property
+    def signal(self):
+        """Process signal, or None."""
+        s = getattr(self.proc, "signal", None)
+        if s is None:
+            rtn = self.returncode
+            if rtn is not None and rtn != 0:
+                s = (-1*rtn, os.WCOREDUMP(rtn))
+        return s
+
     def send_signal(self, signal):
         """Dispatches to Popen.send_signal()."""
         dt = 0.0
@@ -1982,7 +1992,8 @@ class CommandPipeline:
             if core:
                 sig_str += ' (core dumped)'
             print(sig_str, file=sys.stderr)
-            self.errors += sig_str + '\n'
+            if self.errors is not None:
+                self.errors += sig_str + '\n'
 
     def _apply_to_history(self):
         """Applies the results to the current history object."""