clean up temp file after run (#9356)

* clean up temp file after run

* use tempfile

Author: xiangyan99

sdk/core/azure-core/tests/test_retry_policy.py

@@ -19,6 +19,8 @@
     HttpResponse,
     HttpTransport,
 )
+import tempfile
+import os
 
 def test_retry_code_class_variables():
     retry_policy = RetryPolicy()
@@ -141,17 +143,19 @@ def send(self, request, **kwargs):  # type: (PipelineRequest, Any) -> PipelineRe
                     assert not position
                     return HttpResponse(request, None)
 
-    file_name = 'test_retry_seekable_file'
-    with open(file_name, "w+") as f:
-        f.write('Lots of dataaaa')
+    file = tempfile.NamedTemporaryFile(delete=False)
+    file.write(b'Lots of dataaaa')
+    file.close()
     http_request = HttpRequest('GET', 'http://127.0.0.1/')
     headers = {'Content-Type': "multipart/form-data"}
     http_request.headers = headers
-    form_data_content = {
-        'fileContent': open(file_name, 'rb'),
-        'fileName': file_name,
-    }
-    http_request.set_formdata_body(form_data_content)
-    http_retry = RetryPolicy(retry_total = 1)
-    pipeline = Pipeline(MockTransport(), [http_retry])
-    pipeline.run(http_request)
+    with open(file.name, 'rb') as f:
+        form_data_content = {
+            'fileContent': f,
+            'fileName': f.name,
+        }
+        http_request.set_formdata_body(form_data_content)
+        http_retry = RetryPolicy(retry_total=1)
+        pipeline = Pipeline(MockTransport(), [http_retry])
+        pipeline.run(http_request)
+    os.unlink(f.name)