fix: path to pdf file

fet2020/rental/utils.py

@@ -1,6 +1,6 @@
 import io
-from pathlib import Path
 
+from django.contrib.staticfiles import finders
 from django.core.files import File
 from pypdf import PdfReader, PdfWriter
 
@@ -46,8 +46,8 @@ def generate_rental_pdf(rental: Rental) -> bool:
     )
 
     # Write data in pdf
-    pdf_path = Path(Path(__file__).parent) / "static/rental/Verleihformular.pdf"
-    reader = PdfReader(pdf_path)
+    pdf_path_str = finders.find("rental/Verleihformular.pdf")
+    reader = PdfReader(pdf_path_str)
     writer = PdfWriter()
     writer.append(reader)
 
@@ -58,6 +58,7 @@ def generate_rental_pdf(rental: Rental) -> bool:
 
     with io.BytesIO() as bytes_stream:
         writer.write(bytes_stream)
+        bytes_stream.seek(0)
 
         # Save pdf in rental
         rental_name = f"Verleihformular-{str(rental.pk).zfill(4)}.pdf"