prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  test_multiple_heads is not raising the expected error
  **Describe the bug**
  <!-- A clear and concise description of what the bug is. -->
  On having multiple heads, the travis build fails with error -
  ```
  error: Hooks handler process 'dredd-hooks-python ./tests/hook_main.py' exited with status: 1
  warn: Hook handling timed out.
  error: Hooks handler process 'dredd-hooks-python ./tests/hook_main.py' exited with status: 1
  info: Backend server process exited
  The command "dredd" failed and exited with 1 during .
  ```
  It should raise error as expected in - https://github.com/fossasia/open-event-server/blob/development/scripts/test_multiple_heads.sh
  
  **Expected behavior**
  <!-- A clear and concise description of what you expected to happen. -->
  Expected error should be raised - `Error: Multiple Migration Heads`
  
  <!-- If applicable, add stacktrace to help explain your problem. -->
  
  
  **Additional context**
  <!-- Add any other context about the problem here. -->
  On it
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `migrations/versions/rev-2021-01-07-05:19:49-3b29ea38f0cb_.py`
  Content:
  ```
  1 """empty message
  2 
  3 Revision ID: 3b29ea38f0cb
  4 Revises: 2d0760003a8a
  5 Create Date: 2021-01-07 05:19:49.749923
  6 
  7 """
  8 
  9 from alembic import op
  10 import sqlalchemy as sa
  11 import sqlalchemy_utils
  12 
  13 
  14 # revision identifiers, used by Alembic.
  15 revision = '3b29ea38f0cb'
  16 down_revision = '2d0760003a8a'
  17 
  18 
  19 def upgrade():
  20     # ### commands auto generated by Alembic - please adjust! ###
  21     op.add_column('speaker', sa.Column('rank', sa.Integer(), nullable=False, server_default='0'))
  22     # ### end Alembic commands ###
  23 
  24 
  25 def downgrade():
  26     # ### commands auto generated by Alembic - please adjust! ###
  27     op.drop_column('speaker', 'rank')
  28     # ### end Alembic commands ###
  29
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/migrations/versions/rev-2021-01-07-05:19:49-3b29ea38f0cb_.py b/migrations/versions/rev-2021-01-07-05:19:49-3b29ea38f0cb_.py
  --- a/migrations/versions/rev-2021-01-07-05:19:49-3b29ea38f0cb_.py
  +++ b/migrations/versions/rev-2021-01-07-05:19:49-3b29ea38f0cb_.py
  @@ -13,7 +13,7 @@
   
   # revision identifiers, used by Alembic.
   revision = '3b29ea38f0cb'
  -down_revision = '2d0760003a8a'
  +down_revision = '4e61d4df3516'
   
   
   def upgrade():
  
verification_info: {"golden_diff": "diff --git a/migrations/versions/rev-2021-01-07-05:19:49-3b29ea38f0cb_.py b/migrations/versions/rev-2021-01-07-05:19:49-3b29ea38f0cb_.py\n--- a/migrations/versions/rev-2021-01-07-05:19:49-3b29ea38f0cb_.py\n+++ b/migrations/versions/rev-2021-01-07-05:19:49-3b29ea38f0cb_.py\n@@ -13,7 +13,7 @@\n \n # revision identifiers, used by Alembic.\n revision = '3b29ea38f0cb'\n-down_revision = '2d0760003a8a'\n+down_revision = '4e61d4df3516'\n \n \n def upgrade():\n", "issue": "test_multiple_heads is not raising the expected error\n**Describe the bug**\r\n<!-- A clear and concise description of what the bug is. -->\r\nOn having multiple heads, the travis build fails with error -\r\n```\r\nerror: Hooks handler process 'dredd-hooks-python ./tests/hook_main.py' exited with status: 1\r\nwarn: Hook handling timed out.\r\nerror: Hooks handler process 'dredd-hooks-python ./tests/hook_main.py' exited with status: 1\r\ninfo: Backend server process exited\r\nThe command \"dredd\" failed and exited with 1 during .\r\n```\r\nIt should raise error as expected in - https://github.com/fossasia/open-event-server/blob/development/scripts/test_multiple_heads.sh\r\n\r\n**Expected behavior**\r\n<!-- A clear and concise description of what you expected to happen. -->\r\nExpected error should be raised - `Error: Multiple Migration Heads`\r\n\r\n<!-- If applicable, add stacktrace to help explain your problem. -->\r\n\r\n\r\n**Additional context**\r\n<!-- Add any other context about the problem here. -->\r\nOn it\n", "before_files": [{"content": "\"\"\"empty message\n\nRevision ID: 3b29ea38f0cb\nRevises: 2d0760003a8a\nCreate Date: 2021-01-07 05:19:49.749923\n\n\"\"\"\n\nfrom alembic import op\nimport sqlalchemy as sa\nimport sqlalchemy_utils\n\n\n# revision identifiers, used by Alembic.\nrevision = '3b29ea38f0cb'\ndown_revision = '2d0760003a8a'\n\n\ndef upgrade():\n    # ### commands auto generated by Alembic - please adjust! ###\n    op.add_column('speaker', sa.Column('rank', sa.Integer(), nullable=False, server_default='0'))\n    # ### end Alembic commands ###\n\n\ndef downgrade():\n    # ### commands auto generated by Alembic - please adjust! ###\n    op.drop_column('speaker', 'rank')\n    # ### end Alembic commands ###\n", "path": "migrations/versions/rev-2021-01-07-05:19:49-3b29ea38f0cb_.py"}], "after_files": [{"content": "\"\"\"empty message\n\nRevision ID: 3b29ea38f0cb\nRevises: 2d0760003a8a\nCreate Date: 2021-01-07 05:19:49.749923\n\n\"\"\"\n\nfrom alembic import op\nimport sqlalchemy as sa\nimport sqlalchemy_utils\n\n\n# revision identifiers, used by Alembic.\nrevision = '3b29ea38f0cb'\ndown_revision = '4e61d4df3516'\n\n\ndef upgrade():\n    # ### commands auto generated by Alembic - please adjust! ###\n    op.add_column('speaker', sa.Column('rank', sa.Integer(), nullable=False, server_default='0'))\n    # ### end Alembic commands ###\n\n\ndef downgrade():\n    # ### commands auto generated by Alembic - please adjust! ###\n    op.drop_column('speaker', 'rank')\n    # ### end Alembic commands ###\n", "path": "migrations/versions/rev-2021-01-07-05:19:49-3b29ea38f0cb_.py"}]}