WIP: fix regex escapes

pdf-sign

@@ -434,7 +434,7 @@ def pdfCountPages(filePath):
     return int(fromCmdOutput(["pdfinfo", str(filePath)], "^.*\nPages: +([0-9]+)\n.*$")[1])
 
 def pdfGetSize(filePath):
-    [ignored, w, h, *ignored2]=fromCmdOutput(['pdfinfo', filePath], '^.*\nPage size: +([0-9.]+) x ([0-9.]+) pts( \([A-Za-z0-9]+\))?\n.*$')
+    [ignored, w, h, *ignored2]=fromCmdOutput(['pdfinfo', filePath], '^.*\nPage size: +([0-9.]+) x ([0-9.]+) pts( \\([A-Za-z0-9]+\\))?\n.*$')
     return (float(w), float(h))
 
 def m(pattern, string):