Python Cairo. How to draw a line around arc?

Question

I want to draw a line around my arc but.. I can't. It doesn't fit. It's my first day with cairo, so I don't know much. How do I do it right?

I'm drawing it on a drawing area of pyGTK+3 in linux.

//I want to fill and close_path for the other end as well but I've commented it out so that the problem is more easy to spot.

#include "Stopwatch.h"
#include <iostream>
#include <iomanip>
using namespace std;
Stopwatch::Stopwatch(){
    clock_t startTime = 0;
    clock_t endTime = 0;
    clock_t elapsedTime = 0;
    long miliseconds = 0;
} 

void Stopwatch::Start(){
        startTime = clock();
}
void Stopwatch::Stop(){
        endTime = clock();
}
void Stopwatch::DisplayTimerInfo(){
    long formattedSeconds;
    setprecision(4);

    seconds = (endTime - startTime) / CLOCKS_PER_SEC;
    miliseconds = (endTime - startTime) / (CLOCKS_PER_SEC / 1000);

    formattedSeconds = miliseconds / 1000;
    cout << formattedSeconds << endl;

    system("pause");    
}