Remove unused exception variable
Client: Python
Patch: Kevin Wojniak

This closes #1912

Fixes MSVC warning seen in logs:
> [00:11:03] src\ext/protocol.tcc(177): warning C4101: 'ex': unreferenced
> local variable [C:\projects\build\MSVC2015\x86\lib\py\python_build.vcxproj]
diff --git a/lib/py/src/ext/protocol.tcc b/lib/py/src/ext/protocol.tcc
index e15df7e..ede2bb4 100644
--- a/lib/py/src/ext/protocol.tcc
+++ b/lib/py/src/ext/protocol.tcc
@@ -174,7 +174,7 @@
   if (output_->buf.capacity() < need) {
     try {
       output_->buf.reserve(need);
-    } catch (std::bad_alloc& ex) {
+    } catch (std::bad_alloc&) {
       PyErr_SetString(PyExc_MemoryError, "Failed to allocate write buffer");
       return false;
     }