stages/email: fix loading of static files when path is a directory

passbook/stages/email/templatetags/passbook_stages_email.py

@@ -12,7 +12,7 @@ register = template.Library()
 def inline_static_ascii(path: str) -> str:
     """Inline static asset. Doesn't check file contents, plain text is assumed.
     If no file could be found, original path is returned"""
-    result = finders.find(path)
+    result = Path(finders.find(path))
     if result:
         with open(result) as _file:
             return _file.read()
@@ -23,10 +23,9 @@ def inline_static_ascii(path: str) -> str:
 def inline_static_binary(path: str) -> str:
     """Inline static asset. Uses file extension for base64 block. If no file could be found,
     path is returned."""
-    result = finders.find(path)
-    suffix = Path(path).suffix
-    if result:
+    result = Path(finders.find(path))
+    if result and result.is_file():
         with open(result) as _file:
-            b64content = b64encode(_file.read())
-            return f"data:image/{suffix};base64,{b64content.decode('utf-8')}"
+            b64content = b64encode(_file.read().encode())
+            return f"data:image/{result.suffix};base64,{b64content.decode('utf-8')}"
     return path