do not put entire blob value into error message, it might be megabytes

Change-Id: Ib94701022ea864b4d77d2ac632a8b6d74e8b2e16
Reviewed-on: https://forge.frm2.tum.de/review/c/secop/frappy/+/37842
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>
Reviewed-by: Georg Brandl <g.brandl@fz-juelich.de>
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>

frappy/datatypes.py

@@ -587,10 +587,10 @@ class BLOBType(DataType):
         size = len(value)
         if size < self.minbytes:
             raise RangeError(
-                f'{value!r} must be at least {self.minbytes} bytes long!')
+                f'{shortrepr(value)!r} (length {size}) must be at least {self.minbytes} bytes long')
         if size > self.maxbytes:
             raise RangeError(
-                f'{value!r} must be at most {self.maxbytes} bytes long!')
+                f'{shortrepr(value)!r} (length {size}) must be at most {self.maxbytes} bytes long')
         return value
 
     def export_value(self, value):