title: django DB2 inspectdb failure :'NoneType' object is not subscriptable
body: <p>my dev environment is in python 3.6 and virtualenv(virtualenv 15.1.0) and with dependencies below:
      django 2.2
      ibm-db              3.0.1
      ibm-db-django       1.2.0.0</p>
  
  <p>as i used "(env_django2) λ python manage.py check", it return "System check identified no issues (0 silenced)." that is no problom.</p>
  
  <p>however, when i used "python manage.py inspectdb --database db2 DEMO.DEMOUSER", it return like these below:</p>
  
  <pre><code>(env_django2) λ python manage.py inspectdb --database db2 DEMO.DEMOUSER
  # This is an auto-generated Django model module.
  # You'll have to do the following manually to clean this up:
  #   * Rearrange models' order
  #   * Make sure each model has one field with primary_key=True
  #   * Make sure each ForeignKey has `on_delete` set to the desired behavior.
  #   * Remove `managed = False` lines if you wish to allow Django to create, modify, and delete the table
  # Feel free to rename the models, but don't rename db_table values or field names.
  from django.db import models
  # Unable to inspect table 'DEMO.DEMOUSER'
  # The error was: 'NoneType' object is not subscriptable
  </code></pre>
  
  <p>this is my db2 setting:</p>
  
  <pre><code> DATABASES = {
      'default': {
          'ENGINE': 'django.db.backends.sqlite3',
          'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
      },
      'db2':{
          'ENGINE': 'ibm_db_django',
          'NAME': 'test',
          'USER': 'db2inst1',
          'PASSWORD': 'XXXXXX',
          'HOST': 'XX.XXX.XXX.XXX',
          'PORT': 'XXXXX',
          'PCONNECT':True,
      }
  }
  </code></pre>
  
  <p>and i had test it by coding like these below, and that is no problom.</p>
  
  <pre><code>with connections['db2'].cursor() as cursor:
      cursor.execute("""
                      select * from DEMO.DEMOUSER
                    """)
      columns = [col[0] for col in cursor.description]
      listResult = [dict(zip(columns, row)) for row in cursor.fetchall()]
      print(listResult)
  </code></pre>
  
  <p>so my question is how can i make the inspectdb work?</p>
  
  <p>i have check inspectdb.py, and i found that </p>
  
  <pre><code>table_description = connection.introspection.get_table_description(cursor, table_name)
  except Exception as e:
      yield "# Unable to inspect table '%s'" % table_name
  </code></pre>
  
  <p>func get_table_description will invole the code below:</p>
  
  <pre><code>sql = "SELECT TYPE FROM SYSIBM.SYSTABLES WHERE CREATOR='%(schema)s' AND NAME='%(table)s'" % {'schema': schema.upper(), 'table': table_name.upper()}
  </code></pre>
  
  <p>it seem i didn't set the table and schema name right.</p>
  
  <p>ok, i have to go to sleep, very tired.</p>
  
  <p>2020.3.13 update........</p>
  
  <p>so when i readed the code in ibm_db_django\introspection.py, i found that below:</p>
  
  <pre><code>schema = cursor.connection.get_current_schema() 
  </code></pre>
  
  <p>that mean, ibm_db_django will get the schema by default, which is your user name setted in django's setting file. so it will always set the table name like 'db2inst1.DEMO.DEMOUSER' in my case. u can't change the schema by yourself.</p>
  
  <p>as i know, setting the schema immutable is unreasonable,because the schema and user was different things in db2 unlike oracle. everyone can use the granted schema.</p>
  
  <p>hence, i had to change the code like these,so that i can set my schema correctly:</p>
  
  <pre><code># change the code below
  #schema = cursor.connection.get_current_schema()
  print( '-----------change by HK 20200313-----------------')
  if len(table_name.split('.')) == 2:
      cursor.connection.set_current_schema(table_name.split('.')[0].upper())
      table_name = table_name.split('.')[1]
  
  schema = cursor.connection.get_current_schema()
  print('----------------- HK TEST schema:%s'%schema) 
  
  
  # change the code below
  #cursor.execute( "SELECT * FROM %s FETCH FIRST 1 ROWS ONLY" % qn( table_name ) )
  sql = "SELECT * FROM %s FETCH FIRST 1 ROWS ONLY" % ( schema+'.'+table_name )
  print('------------ HK TEST LOG:%s'%sql)
  cursor.execute( sql )
  </code></pre>
  
  <p>so the problem had been solved,however,another emerged !!
  when i typed the command "python manage.py inspectdb --database db2 DEMO.DEMOUSER", it show below:</p>
  
  <pre><code>class DemoDemouser(models.Model):
  Traceback (most recent call last):
    File "manage.py", line 21, in &lt;module&gt;
      main()
    File "manage.py", line 17, in main
      execute_from_command_line(sys.argv)
    File "D:\MyProject\python\django-sample\env_django2\lib\site-packages\django\core\management\__init__.py", line 381, in execute_from_command_line
      utility.execute()
    File "D:\MyProject\python\django-sample\env_django2\lib\site-packages\django\core\management\__init__.py", line 375, in execute
      self.fetch_command(subcommand).run_from_argv(self.argv)
    File "D:\MyProject\python\django-sample\env_django2\lib\site-packages\django\core\management\base.py", line 323, in run_from_argv
      self.execute(*args, **cmd_options)
    File "D:\MyProject\python\django-sample\env_django2\lib\site-packages\django\core\management\base.py", line 364, in execute
      output = self.handle(*args, **options)
    File "D:\MyProject\python\django-sample\env_django2\lib\site-packages\django\core\management\commands\inspectdb.py", line 34, in handle
      for line in self.handle_inspection(options):
    File "D:\MyProject\python\django-sample\env_django2\lib\site-packages\django\core\management\commands\inspectdb.py", line 102, in handle_inspection
      column_name = row.name
  AttributeError: 'list' object has no attribute 'name'
  </code></pre>
  
  <p>checking inspectdb.py，i find out the answer. the description of specified table ,returned from the func in introspection.py implemented by ibm_db_django, is different from inspectdb.py in django 2.2.</p>
  
  <p>so check it with django release history and ibm_db_ango.
  ibm_db_ango 1.2 released in 2018.4.3, django 2.2 released in 2019.3.</p>
  
  <p>it seem  django 2.2 dont support the ibm_db_ango 1.2(the latest version)</p>
  
  <p>therefore i had to install django 2.0 instead. </p>
  
  <p>finally it work!!!.</p>