Split persister errors into CassetteNotFoundError and CassetteDecodeError (#681)

vcr/cassette.py

@@ -11,7 +11,7 @@ from ._handle_coroutine import handle_coroutine
 from .errors import UnhandledHTTPRequestError
 from .matchers import get_matchers_results, method, requests_match, uri
 from .patch import CassettePatcherBuilder
-from .persisters.filesystem import FilesystemPersister
+from .persisters.filesystem import CassetteDecodeError, CassetteNotFoundError, FilesystemPersister
 from .record_mode import RecordMode
 from .serializers import yamlserializer
 from .util import partition_dict
@@ -352,7 +352,7 @@ class Cassette:
                 self.append(request, response)
             self.dirty = False
             self.rewound = True
-        except ValueError:
+        except (CassetteDecodeError, CassetteNotFoundError):
             pass
 
     def __str__(self):

vcr/persisters/filesystem.py

@@ -5,17 +5,25 @@ from pathlib import Path
 from ..serialize import deserialize, serialize
 
 
+class CassetteNotFoundError(FileNotFoundError):
+    pass
+
+
+class CassetteDecodeError(ValueError):
+    pass
+
+
 class FilesystemPersister:
     @classmethod
     def load_cassette(cls, cassette_path, serializer):
         cassette_path = Path(cassette_path)  # if cassette path is already Path this is no operation
         if not cassette_path.is_file():
-            raise ValueError("Cassette not found.")
+            raise CassetteNotFoundError()
         try:
             with cassette_path.open() as f:
                 data = f.read()
-        except UnicodeEncodeError as err:
-            raise ValueError("Can't read Cassette, Encoding is broken") from err
+        except UnicodeDecodeError as err:
+            raise CassetteDecodeError("Can't read Cassette, Encoding is broken") from err
 
         return deserialize(data, serializer)