symbolize.py: fix exception when stdin is not a terminal

Commit 6b4fc6752b3c ("symbolize.py: disable terminal local echo") uses
termios functions on stdin unconditionally. Unfortunately, this will
cause an exception when stdin is not a terminal, for instance:

 $ echo Hello | ./script/symbolize.py
 Traceback (most recent call last):
   File "./scripts/symbolize.py", line 497, in <module>
     main()
   File "./scripts/symbolize.py", line 484, in main
     old = termios.tcgetattr(fd)
 termios.error: (25, 'Inappropriate ioctl for device')

Fix the issue by making sure stdin is a TTY before using the termios
functions.

Fixes: 6b4fc6752b3c ("symbolize.py: disable terminal local echo")
Signed-off-by: Jerome Forissier <jerome@forissier.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>

1 files changed, 9 insertions, 5 deletions

diff --git a/scripts/symbolize.py b/scripts/symbolize.py
index b61202d4..5928932d 100755
--- a/scripts/symbolize.py
+++ b/scripts/symbolize.py
@@ -481,16 +481,20 @@ def main():
     symbolizer = Symbolizer(sys.stdout, args.dirs, args.strip_path)
 
     fd = sys.stdin.fileno()
-    old = termios.tcgetattr(fd)
-    new = termios.tcgetattr(fd)
-    new[3] = new[3] & ~termios.ECHO  # lflags
+    isatty = os.isatty(fd)
+    if isatty:
+        old = termios.tcgetattr(fd)
+        new = termios.tcgetattr(fd)
+        new[3] = new[3] & ~termios.ECHO  # lflags
     try:
-        termios.tcsetattr(fd, termios.TCSADRAIN, new)
+        if isatty:
+            termios.tcsetattr(fd, termios.TCSADRAIN, new)
         for line in sys.stdin:
             symbolizer.write(line)
     finally:
         symbolizer.flush()
-        termios.tcsetattr(fd, termios.TCSADRAIN, old)
+        if isatty:
+            termios.tcsetattr(fd, termios.TCSADRAIN, old)
 
 
 if __name__ == "__main__":