Does a defendant have to obtain a certificate of probable cause to appeal from a judgment of conviction upon a plea of no contest?

As a general matter, "[a] defendant may not appeal 'from a judgment of conviction upon a plea of guilty or nolo contendere,' unless he has obtained a certificate of probable cause. ( 1237.5, subd. (b); see People v. Buttram (2003) 30 Cal.4th 773, 790 [134 Cal.Rptr.2d 571, 69 P.3d 420] (Buttram) [ 1237.5's purpose is 'to weed out frivolous and vexatious appeals from pleas of guilty or no contest, before clerical and judicial resources are wasted'].) Exempt from this certificate requirement are postplea claims,

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