import java.util.*;
import java.util.regex.*;
import java.lang.*;
import java.io.*;
 
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String unescapedStr = "Retrying for error: [[\"billing\",\\{u'non_field_errors': [u'Invalid payment email provided']}\"]]";
		String pattern = "Retrying for error:.*\\[u'([^']+)";
		Pattern r = Pattern.compile(pattern);
		Matcher m = r.matcher(unescapedStr);
		if (m.find()) {
		  System.out.println(m.group(1));
		}
	}
}

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