Force prettytable==0.5

prettytable 0.6 was released recently and removed the printt() method.
All non-pinned prettytable projects (all of them) are now broken.  This
forces a pre-loaded prettytable 0.5 package in order to allow the real
fix (removing printt() calls) to proceed.

Change-Id: Iacf24b8474f12b28090329496720767281181d7e
diff --git a/files/pips/general b/files/pips/general
new file mode 100644
index 0000000..f740306
--- /dev/null
+++ b/files/pips/general
@@ -0,0 +1 @@
+prettytable==0.5