DBT requires Python 3.6.2+

[Fokko]

Describe the bug

A clear and concise description of what the bug is. What command did you run? What happened?

From a confused user on Slack, which used Python 3.6.0, got the following error:

Traceback (most recent call last):
  File "/tmp/venv/bin/dbt", line 5, in <module>
    from dbt.main import main
  File "/tmp/venv/lib/python3.6/site-packages/dbt/main.py", line 10, in <module>
    import dbt.version
  File "/tmp/venv/lib/python3.6/site-packages/dbt/version.py", line 5, in <module>
    import dbt.exceptions
  File "/tmp/venv/lib/python3.6/site-packages/dbt/exceptions.py", line 3, in <module>
    from typing import NoReturn, Optional
ImportError: cannot import name 'NoReturn'

As the NoReturn is introduced in Python 3.6.2: https://docs.python.org/3/library/typing.html#typing.NoReturn

Steps To Reproduce

In as much detail as possible, please provide steps to reproduce the issue. Sample data that triggers the issue, example model code, etc is all very helpful here.

Run DBT 0.16.1 with Python <3.6.2:

Python 3.6.0:

MacBook-Pro-van-Fokko:home-analytics fokkodriesprong$ docker run -t -i python:3.6.0 python -c "from typing import NoReturn"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: cannot import name 'NoReturn'

Python 3.6.1:

MacBook-Pro-van-Fokko:home-analytics fokkodriesprong$ docker run -t -i python:3.6.1 python -c "from typing import NoReturn"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: cannot import name 'NoReturn'

Python 3.6.2:

MacBook-Pro-van-Fokko:home-analytics fokkodriesprong$ docker run -t -i python:3.6.2 python -c "from typing import NoReturn"

Expected behavior

A clear and concise description of what you expected to happen.

Screenshots and log output

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System information

Which database are you using dbt with?

• postgres
• redshift
• bigquery
• snowflake
• other (specify: ____________)

The output of dbt --version:

root@8a3491679f36:/# dbt --version
installed version: 0.16.1
   latest version: 0.16.1

The operating system you're using:

OSX, see docker examples above

Additional context

Add any other context about the problem here.