python
diff --git a/‎cherry_picker/cherry_picker/cherry_picker.py
Copy file name to clipboardExpand all lines: cherry_picker/cherry_picker/cherry_picker.py
+9-1Lines changed: 9 additions & 1 deletion b/‎cherry_picker/cherry_picker/cherry_picker.py
Copy file name to clipboardExpand all lines: cherry_picker/cherry_picker/cherry_picker.py
+9-1Lines changed: 9 additions & 1 deletion
@@ -421,8 +421,16 @@ def get_base_branch(cherry_pick_branch):
 
     if prefix != 'backport':
         raise ValueError('branch name is not prefixed with "backport-".  Is this a cherry_picker branch?')
+
     if not re.match('[0-9a-f]{7,40}', sha):
-        raise ValueError('branch name has an invalid sha')
+        raise ValueError(f'branch name has an invalid sha: {sha}')
+
+    cmd = ['git', 'log', '-r', sha]
+    try:
+        subprocess.check_output(cmd, stderr=subprocess.STDOUT)
+    except subprocess.SubprocessError:
+        raise ValueError(f'The sha listed in the branch name, {sha}, is not present in the repository')
+
     # Subject the parsed base_branch to the same tests as when we generated it
     # This throws a ValueError if the base_branch doesn't need our requirements
     version_from_branch(base_branch)