Tests for USE of non-dolt dbs

go/libraries/doltcore/sqle/dsess/session.go

@@ -972,7 +972,9 @@ func (d *DoltSession) SwitchWorkingSet(
 func (d *DoltSession) UseDatabase(ctx *sql.Context, db sql.Database) error {
 	sdb, ok := db.(SqlDatabase)
 	if !ok {
-		return fmt.Errorf("expected a SqlDatabase, got %T", db)
+		// Could be an externally provided db such as `mysql` or `information_schema`, in which case there's nothing for 
+		// this hook to do
+		return nil
 	}
 
 	branchState, ok, err := d.lookupDbState(ctx, sdb.RevisionQualifiedName())

integration-tests/bats/sql.bats

@@ -2855,3 +2855,26 @@ SQL
     [ "$status" -eq 1 ]
     [[ "$output" =~ "provided --use-db dba does not exist or is not a directory" ]] || false
 }
+
+@test "sql: USE information schema and mysql databases" {
+    run dolt sql <<SQL
+USE information_schema;
+show tables;
+SQL
+
+    # spot check result
+    [ "$status" -eq 0 ]
+    [[ "$output" =~ "Database changed" ]] || false
+    [[ "$output" =~ "columns" ]] || false
+
+    run dolt sql <<SQL
+USE mysql;
+show tables;
+SQL
+
+    # spot check result
+    [ "$status" -eq 0 ]
+    [[ "$output" =~ "Database changed" ]] || false
+    [[ "$output" =~ "role_edges" ]] || false
+    
+}