Always close pycurl instance

The class has a `__del__` method, but that's not always guaranteed to
run in a timely fashion.

pulsar/client/transport/curl.py

@@ -60,6 +60,7 @@ def execute(self, url, method=None, data=None, input_path=None, output_path=None
             if not output_path:
                 return buf.getvalue()
         finally:
+            c.close()
             buf.close()
 
 
@@ -69,13 +70,16 @@ def post_file(url, path):
         # wrap it in a better one.
         message = NO_SUCH_FILE_MESSAGE % (path, url)
         raise Exception(message)
-    c = _new_curl_object_for_url(url)
-    c.setopt(c.HTTPPOST, [("file", (c.FORM_FILE, path.encode('ascii')))])
-    c.perform()
-    status_code = c.getinfo(HTTP_CODE)
-    if int(status_code) != 200:
-        message = POST_FAILED_MESSAGE % (url, status_code)
-        raise Exception(message)
+    try:
+        c = _new_curl_object_for_url(url)
+        c.setopt(c.HTTPPOST, [("file", (c.FORM_FILE, path.encode('ascii')))])
+        c.perform()
+        status_code = c.getinfo(HTTP_CODE)
+        if int(status_code) != 200:
+            message = POST_FAILED_MESSAGE % (url, status_code)
+            raise Exception(message)
+    finally:
+        c.close()
 
 
 def get_size(url) -> int:
@@ -122,6 +126,7 @@ def get_file(url, path: str):
             message = GET_FAILED_MESSAGE % (url, status_code)
             raise Exception(message)
     finally:
+        c.close()
         buf.close()