title: Dask read_sql_table throws error AttributeError: 'Connection' object has no attribute '_instantiate_plugins'
body: <pre><code>from sqlalchemy import create_engine
  sql_engine = create_engine('oracle+cx_oracle://user:password@environment')
  connection = sql_engine.connect()
  # works with PANDAS?
  import pandas as pd
  pd.read_sql_table('table', connection)
  </code></pre>
  
  <p>The above gives expected output.  Now for Dask...</p>
  
  <pre><code>import dask.dataframe as dd
  dd.read_sql_table('table', connection)
  </code></pre>
  
  <p>...which gives...</p>
  
  <blockquote>
    <p>--------------------------------------------------------------------------- TypeError                                 Traceback (most recent call
    last)  in 
    ----> 1 dd.read_sql_table('qsi_run_info_int', connection)#, 'hedis_version_key')</p>
    
    <p>TypeError: read_sql_table() missing 1 required positional argument:
    'index_col'</p>
  </blockquote>
  
  <p>...and adding column to index on via...</p>
  
  <pre><code>dd.read_sql_table('table', connection, 'column_to_index_on')
  </code></pre>
  
  <p>...gives...</p>
  
  <blockquote>
    <p>--------------------------------------------------------------------------- AttributeError                            Traceback (most recent call
    last)  in 
    ----> 1 dd.read_sql_table('qsi_run_info_int', connection, 'hedis_version_key')</p>
    
    <p>~.conda\envs\test_dask\lib\site-packages\dask\dataframe\io\sql.py in
    read_sql_table(table, uri, index_col, divisions, npartitions, limits,
    columns, bytes_per_chunk, head_rows, schema, meta, engine_kwargs,
    **kwargs)
         98         raise ValueError("Must specify index column to partition on")
         99     engine_kwargs = {} if engine_kwargs is None else engine_kwargs
    --> 100     engine = sa.create_engine(uri, **engine_kwargs)
        101     m = sa.MetaData()
        102     if isinstance(table, string_types):</p>
    
    <p>~.conda\envs\test_dask\lib\site-packages\sqlalchemy\engine__init__.py
    in create_engine(*args, **kwargs)
        433     strategy = kwargs.pop("strategy", default_strategy)
        434     strategy = strategies.strategies[strategy]
    --> 435     return strategy.create(*args, **kwargs)
        436 
        437 </p>
    
    <p>~.conda\envs\test_dask\lib\site-packages\sqlalchemy\engine\strategies.py
    in create(self, name_or_url, **kwargs)
         54         u = url.make_url(name_or_url)
         55 
    ---> 56         plugins = u._instantiate_plugins(kwargs)
         57 
         58         u.query.pop("plugin", None)</p>
    
    <p>AttributeError: 'Connection' object has no attribute
    '_instantiate_plugins'</p>
  </blockquote>
  
  <p>What to try next?</p>