Protect tests/writetofile.py from test discovery

IPython/frontend/terminal/console/tests/writetofile.py

@@ -17,16 +17,17 b" If INPUT is '-', stdin is used."
 
 """
 
-import sys
-from IPython.utils.py3compat import PY3
-(inpath, outpath) = sys.argv[1:]
-
-if inpath == '-':
-    if PY3:
-        infile = sys.stdin.buffer
+if __name__ == '__main__':
+    import sys
+    from IPython.utils.py3compat import PY3
+    (inpath, outpath) = sys.argv[1:]
+
+    if inpath == '-':
+        if PY3:
+            infile = sys.stdin.buffer
+        else:
+            infile = sys.stdin
     else:
-        infile = sys.stdin
-else:
-    infile = open(inpath, 'rb')
+        infile = open(inpath, 'rb')
 
-open(outpath, 'w+b').write(infile.read())
+    open(outpath, 'w+b').write(infile.read())