In this case, you should identify the stale connection and update the respective dataset/s to a working connection or a dummy connection that exists as you can later remap these when importing the project.
The error should indicate the connection name to list all datasets using that connection you can run the following in a Notebook :
client = dataiku.api_client()
# Get project using the ProjectKey
proj = client.get_project('project-name')
# List all datasets within the project
my_list = proj.list_datasets()
# set name of the connection that is missing
bad_connection = "name-of-deleted-connection"
# For each filesystem managed dataset, change connection to new filesystem connection
for my_data in my_list:
dataset = proj.get_dataset(my_data["name"])
my_def = dataset.get_definition()
if my_def["params"]["connection"] == bad_connection:
Then you can edit the connection to a valid connection for the dataset names that are printed.