fixup! client: Refactor openClientByURL for easier testing

- no need to pass DriverOptions into parseURL - it is only zurl that is
  parsed, and also DriverOptions should not be changed by the opener.

- no need to document "If anything fails within this process an error
  and nil are returned." because that is standard omnipresent Go convention.

go/neo/client.go

@@ -416,11 +416,15 @@ func (c *Client) Iterate(ctx context.Context, tidMin, tidMax zodb.Tid) zodb.ITxn
 func openClientByURL(ctx context.Context, u *url.URL, opt *zodb.DriverOptions) (_ zodb.IStorageDriver, _ zodb.Tid, err error) {
 	defer task.Runningf(&ctx, "neo: open %s", u)(&err)
 
-	urlinfo, err := parseURL(ctx, u, opt)
+	urlinfo, err := parseURL(ctx, u)
 	if err != nil {
 		return nil, zodb.InvalidTid, err
 	}
 
+	if !opt.ReadOnly {
+		return nil, zodb.InvalidTid, fmt.Errorf("TODO write mode not implemented")
+	}
+
 	net, err := neonet.Join(ctx, urlinfo.netcfg)
 	if err != nil {
 		return nil, zodb.InvalidTid, err
@@ -477,9 +481,8 @@ func openClientByURL(ctx context.Context, u *url.URL, opt *zodb.DriverOptions) (
 }
 
 // parseURL extracts information from a NEO URI and puts this information into
-// a urlInfo and the DriverOptions. If anything fails within this process
-// an error and nil are returned.
-func parseURL(ctx context.Context, u *url.URL, opt *zodb.DriverOptions) (urlinfo *urlInfo, err error) {
+// a urlInfo.
+func parseURL(ctx context.Context, u *url.URL) (urlinfo *urlInfo, err error) {
 	// neo(s)://[credentials@]master1,master2,...,masterN/name?options
 
 	var ssl bool
@@ -538,10 +541,6 @@ func parseURL(ctx context.Context, u *url.URL, opt *zodb.DriverOptions) (urlinfo
 		return nil, fmt.Errorf("invalid query: %v", q)
 	}
 
-	if !opt.ReadOnly {
-		return nil, fmt.Errorf("TODO write mode not implemented")
-	}
-
 	masterAddr := u.Host
 
 	return &urlInfo{masterAddr, name, netcfg}, nil