Python API: Fix error message typo.

Change-Id: Icb67797a91a5929e57a08b79adeca226fee09de3
Signed-off-by: Ole Troan <ot@cisco.com>
diff --git a/src/vpp-api/python/vpp_papi.py b/src/vpp-api/python/vpp_papi.py
index 489731a..55dda10 100644
--- a/src/vpp-api/python/vpp_papi.py
+++ b/src/vpp-api/python/vpp_papi.py
@@ -442,7 +442,7 @@
         size = ffi.new("int *")
         rv = vpp_api.vac_read(mem, size, self.read_timeout)
         if rv:
-            raise IOError(rv, 'vac_read filed')
+            raise IOError(rv, 'vac_read failed')
         msg = bytes(ffi.buffer(mem[0], size[0]))
         vpp_api.vac_free(mem[0])
         return msg