BaseTools:Fix build tools print traceback info issue

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2610

We meet a case that the DEC file declaring the PCD isn't
included in the INF.it cause build tools report Traceback error.

Remove raise statements that generate Tracebacks that were only
intended for development/debug. With the raise statements removed
proper error messages are shown.

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Zhiju.Fan <zhijux.fan@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>