BigQuery: magic cell in IPython/Jupyter should hide bad query tracebacks

[brianquinlan]

Incorrect user queries using IPython/Jupyter magic cells generate a large traceback. For example:

In [1]:  %%bigquery
           SELECT badname
           FROM mytable
---------------------------------------------------------------------------
BadRequest                                Traceback (most recent call last)
<ipython-input-4-f03917bb6736> in <module>
----> 1 get_ipython().run_cell_magic('bigquery', '', 'SELECT badname\nFROM mytable\n')

~/cloud/bigmerge/venv/lib/python3.6/site-packages/IPython/core/interactiveshell.py in run_cell_magic(self, magic_name, line, cell)
   2321             magic_arg_s = self.var_expand(line, stack_depth)
   2322             with self.builtin_trap:
-> 2323                 result = fn(magic_arg_s, cell)
   2324             return result
   2325 

~/cloud/bigmerge/venv/lib/python3.6/site-packages/google/cloud/bigquery/magics.py in _cell_magic(line, query)
    322     job_config.query_parameters = params
    323     job_config.use_legacy_sql = args.use_legacy_sql
--> 324     query_job = _run_query(client, query, job_config)
    325 
    326     if not args.verbose:

~/cloud/bigmerge/venv/lib/python3.6/site-packages/google/cloud/bigquery/magics.py in _run_query(client, query, job_config)
    251             time.time() - start_time), end='')
    252         try:
--> 253             query_job.result(timeout=0.5)
    254             break
    255         except futures.TimeoutError:

~/cloud/bigmerge/venv/lib/python3.6/site-packages/google/cloud/bigquery/job.py in result(self, timeout, retry)
   2735             not complete in the given timeout.
   2736         """
-> 2737         super(QueryJob, self).result(timeout=timeout)
   2738         # Return an iterator instead of returning the job.
   2739         if not self._query_results:

~/cloud/bigmerge/venv/lib/python3.6/site-packages/google/cloud/bigquery/job.py in result(self, timeout)
    697             self._begin()
    698         # TODO: modify PollingFuture so it can pass a retry argument to done().
--> 699         return super(_AsyncJob, self).result(timeout=timeout)
    700 
    701     def cancelled(self):

~/cloud/bigmerge/venv/lib/python3.6/site-packages/google/api_core/future/polling.py in result(self, timeout)
    125             # pylint: disable=raising-bad-type
    126             # Pylint doesn't recognize that this is valid in this case.
--> 127             raise self._exception
    128 
    129         return self._result

BadRequest: 400 Unrecognized name: badname at [1:8]

Since the above code is executed implicitly, it should be hidden from the user and, instead, only the user-relevant part of the error should be shown. Like:

In [1]:  %%bigquery
           SELECT badname
           FROM mytable

Your query contained an error. Unrecognized name: badname at [1:8]