Error while generating screenshot in linux cannot

Problem:

Iam using PyQt4 library to generate screenshots of website.Code is presented below.When iam running for all the urls in a list the screenshots are getting generated for first 50-60 urls after that it is failing with the following error.

cannot connect to X server localhost:10.0

Code Snippet:

class Screenshot(QWebView):
    def __init__(self):
        self.app = QApplication(sys.argv)
        QWebView.__init__(self)
        self._loaded = False
        self.loadFinished.connect(self._loadFinished)

    def capture(self, url, output_file):
        _logger.info('Received url {}'.format(url))
        _start = time.time()
        try:
            #Check for http/https
            if url[0:3] == 'http' or url[0:4] == 'https':
                self.url = url
            else:
                url = 'http://' + url
            self.load(QUrl(url))
            self.wait_load(url)
            # set to webpage size
            frame = self.page().mainFrame()
            self.page().setViewportSize(frame.contentsSize())
            # render image
            image = QImage(self.page().viewportSize(), QImage.Format_ARGB32)
            painter = QPainter(image)
            frame.render(painter)
            painter.end()
            _logger.info('Saving screenshot {} for {}'.format(output_file,url))
            image.save(os.path.join(os.path.dirname(os.path.realpath(__file__)),'data',output_file))
        except Exception as e:
            _logger.error('Error in capturing screenshot {} - {}'.format(url,e))
        _end = time.time()
        _logger.info('Time took for processing url {} - {}'.format(url,_end - _start))

    def wait_load(self,url,delay=1,retry_count=60):
        # process app events until page loaded
        while not self._loaded and retry_count:
            _logger.info('wait_load for url {} retry_count {}'.format(url,retry_count))
            self.app.processEvents()
            time.sleep(delay)
            retry_count -=1
        _logger.info('wait_load for url {} expired'.format(url))
        self._loaded = False

    def _loadFinished(self, result):
        self._loaded = True

Any suggestions on how to solve this?Or is there any alternative approaches to do screenshot of urls.

System Config:

lscpu:
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                16
On-line CPU(s) list:   0-15
Thread(s) per core:    1
Core(s) per socket:    2
Socket(s):             8
NUMA node(s):          8
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 63
Model name:            Intel(R) Xeon(R) CPU E5-2620 v3 @ 2.40GHz
Stepping:              2
CPU MHz:               2399.998
BogoMIPS:              4799.99
Hypervisor vendor:     VMware
Virtualization type:   full
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              15360K
NUMA node0 CPU(s):     0,1
NUMA node1 CPU(s):     2,3
NUMA node2 CPU(s):     4,5
NUMA node3 CPU(s):     6,7
NUMA node4 CPU(s):     8,9
NUMA node5 CPU(s):     10,11
NUMA node6 CPU(s):     12,13
NUMA node7 CPU(s):     14,15
Flags:                 fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts mmx fxsr sse sse2 ss ht syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts nopl xtopology tsc_reliable nonstop_tsc aperfmperf pni pclmulqdq ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx hypervisor lahf_lm epb kaiser cqm_llc cqm_occup_llc dtherm ida arat pln pts