diff --git a/stix_shifter/stix_transmission/src/modules/utils/RestApiClient.py b/stix_shifter/stix_transmission/src/modules/utils/RestApiClient.py
index 220df9fa8..1608c897f 100644
--- a/stix_shifter/stix_transmission/src/modules/utils/RestApiClient.py
+++ b/stix_shifter/stix_transmission/src/modules/utils/RestApiClient.py
@@ -14,58 +14,61 @@ def __init__(self, host, port = None, cert=None, headers={}, url_modifier_functi
             server_ip += ":" + str(port)            
         self.server_ip = server_ip
         self.cert_verify = str(cert_verify).lower() not in ['0', 'f', 'false', 'f', 'n', 'no', 'disable', 'disabled']
-        self.cert_file = None
-        if cert is not None and self.cert_verify:
-            # put key/cert pair into a file to read it later
-            cert_file_name = "cert.pem"
-            with open(cert_file_name, 'w+') as f:
-                try:
-                    f.write(cert)
-                except IOError:
-                    print('Failed to setup certificate')
-
-            self.cert_file = cert_file_name
+        self.cert = cert
         self.headers = headers
         self.url_modifier_function = url_modifier_function
 
-    def __del__(self):
-        try:
-            os.remove('cert.pem')
-        except OSError as e:
-            if e.errno != errno.ENOENT:
-                raise
 
     # This method is used to set up an HTTP request and send it to the server
     def call_api(self, endpoint, method, headers=None, params=[], data=None, urldata=None):
-        url = None
-        actual_headers = self.headers.copy()
-        if headers is not None:
-            for header_key in headers:
-                actual_headers[header_key] = headers[header_key]
-
-        if urldata is not None:
-            urldata = urllib.parse.urlencode(urldata)
-            if '?' in endpoint:
-                endpoint += '&'
-            else:
-                endpoint += '?'
-            endpoint += urldata            
 
-        if self.url_modifier_function is not None:
-            url = self.url_modifier_function(self.server_ip, endpoint, actual_headers)
-        else:
-            url = 'https://' + self.server_ip + '/' + endpoint
+        self.cert_file_name = None
         try:
-            call = getattr(requests, method.lower())
-            response = call(url, headers=actual_headers, cert=self.cert_file, data=data, verify=self.cert_verify)
-            
-            if 'headers' in dir(response) and isinstance(response.headers, collections.Mapping) and 'Content-Type' in response.headers \
-                            and "Deprecated" in response.headers['Content-Type']:
-                print("WARNING: " + response.headers['Content-Type'], file=sys.stderr)
-            return ResponseWrapper(response)
-        except Exception as e:
-            print('exception occured during requesting url: ' + str(e))
-            raise e
+            if self.cert is not None and self.cert_verify:
+                # put key/cert pair into a file to read it later
+                self.cert_file_name = "cert.pem"
+                with open(self.cert_file_name, 'w') as f:
+                    try:
+                        f.write(self.cert)
+                    except IOError:
+                        print('Failed to setup certificate')
+
+            url = None
+            actual_headers = self.headers.copy()
+            if headers is not None:
+                for header_key in headers:
+                    actual_headers[header_key] = headers[header_key]
+
+            if urldata is not None:
+                urldata = urllib.parse.urlencode(urldata)
+                if '?' in endpoint:
+                    endpoint += '&'
+                else:
+                    endpoint += '?'
+                endpoint += urldata            
+
+            if self.url_modifier_function is not None:
+                url = self.url_modifier_function(self.server_ip, endpoint, actual_headers)
+            else:
+                url = 'https://' + self.server_ip + '/' + endpoint
+            try:
+                call = getattr(requests, method.lower())
+                response = call(url, headers=actual_headers, cert=self.cert_file_name, data=data, verify=self.cert_verify)
+                
+                if 'headers' in dir(response) and isinstance(response.headers, collections.Mapping) and 'Content-Type' in response.headers \
+                                and "Deprecated" in response.headers['Content-Type']:
+                    print("WARNING: " + response.headers['Content-Type'], file=sys.stderr)
+                return ResponseWrapper(response)
+            except Exception as e:
+                print('exception occured during requesting url: ' + str(e))
+                raise e
+        finally:
+            if self.cert_file_name is not None:
+                try:
+                    os.remove(self.cert_file_name)
+                except OSError as e:
+                    if e.errno != errno.ENOENT:
+                        raise
 
     # Simple getters that can be used to inspect the state of this client.
     def get_headers(self):