util: strip trailing newline from debugstacktrace message

This makes the function more convenient to use as drop-in replacement for
ui.write & co.

mercurial/util.py

@@ -2871,7 +2871,7 b" def debugstacktrace(msg='stacktrace', sk"
     '''
     if otherf:
         otherf.flush()
-    f.write('%s at:\n' % msg)
+    f.write('%s at:\n' % msg.rstrip())
     for line in getstackframes(skip + 1):
         f.write(line)
     f.flush()

tests/test-debugcommands.t

@@ -129,8 +129,7 b' Test internal debugstacktrace command'
   stacktrace at:
    debugstacktrace.py:10 in * (glob)
    debugstacktrace.py:3  in f
-  hello from g
-   at:
+  hello from g at:
    debugstacktrace.py:10 in * (glob)
    debugstacktrace.py:4  in f
   hi ...