Prevent misbehaving dynamic context plugins from ruining coverage

Author: s0undt3ch

coverage/sqldata.py

@@ -70,6 +70,7 @@
     id integer primary key,
     context text,
     unique (context)
+    ON CONFLICT IGNORE
 );
 
 CREATE TABLE line_bits (

doc/dbschema.rst

@@ -72,6 +72,7 @@ TODO: explain more. Readers: what needs explaining?
         id integer primary key,
         context text,
         unique (context)
+        ON CONFLICT IGNORE
     );
 
     CREATE TABLE line_bits (