fix: move checksum verification into a separate function

Fixes #1

imgsync/distros/base.py

@@ -57,15 +57,6 @@ def _get_file_checksum(self, path, block_size=2**20):
                 buf = f.read(block_size)
         return sha512
 
-    def verify_checksum(
-        self,
-        location,
-        name,
-        checksum,
-    ):
-        """Verify the image's checksum."""
-        # TODO(aloga): not implemented yet
-
     def _download_one(self, url, checksum):
         """Download a file.
 
@@ -99,6 +90,17 @@ def _download_one(self, url, checksum):
                     location.write(block)
                     location.flush()
 
+        self.verify_checksum(location, url, checksum, url)
+
+    def verify_checksum(
+        self,
+        location,
+        name,
+        checksum,
+        url
+    ):
+        """Verify the image's checksum."""
+
         checksum_map = {"sha512": hashlib.sha512, "sha256": hashlib.sha256}
         sha = checksum_map.get(checksum[0])()
         block_size = 2**20