Fix the exception messages

lib/private/files/cache/cache.php

@@ -287,7 +287,7 @@ class Cache {
 				$this->update($id, $data);
 				return $id;
 			} else {
-				throw new \RuntimeException('File entry exists when inserting and does not exist on select... go away');
+				throw new \RuntimeException('File entry could not be inserted with insertIfNotExist() but could also not be selected with getId() in order to perform an update. Please try again.');
 			}
 		}
 	}

lib/private/files/cache/storage.php

@@ -62,7 +62,7 @@ class Storage {
 				if ($row = $result->fetchRow()) {
 					$this->numericId = $row['numeric_id'];
 				} else {
-					throw new \RuntimeException('Storage exists when inserting and does not exist on select... go away');
+					throw new \RuntimeException('Storage could neither be inserted nor be selected from the database');
 				}
 			}
 		}