Use context manager for opening file

bam/cli.py

@@ -1098,13 +1098,13 @@ class bam_commands:
             "file": open(temp_zip, 'rb'),
             }
 
+        with files["file"]:
             r = requests.put(
                     bam_session.request_url("file"),
                     params=payload,
                     auth=(cfg["user"], cfg["password"]),
                     files=files)
 
-        files["file"].close()
         os.remove(temp_zip)
 
         try: