Update app.py

app.py

@@ -206,7 +206,7 @@ If you use this tool for your research, please cite <a href='https://arxiv.org/a
     # If file is uploaded, read in the data and plot it
 if uploaded_file is not None:
     data, wcs = load_file(uploaded_file)
-    os.system('mkdir -p {uploaded_file.name.strip(".fits")')
+    os.system(f'mkdir -p {uploaded_file.name.strip(".fits")}')
 
 if "data" not in locals():
     data = np.zeros((128,128))