Bump astroid from 1.6.4 to 2.0.4

[dependabot-preview]

Bumps astroid from 1.6.4 to 2.0.4.

Changelog

Sourced from astroid's changelog.

What's New in astroid 2.0.4?

Release Date: 2018-08-10

• Make sure that assign nodes can find yield statements in their values

  Close E1111 False Positive With Generators pylint-dev/pylint#2400

What's New in astroid 2.0.3?

Release Date: 2018-08-08

• The environment markers for PyPy were invalid.

What's New in astroid 2.0.2?

Release Date: 2018-08-01

• Stop repeat inference attempt causing a RuntimeError in Python3.7

  Close RuntimeError: generator raised StopIteration pylint-dev/pylint#2317

• infer_call_result can raise InferenceError so make sure to handle that for the call sites
  where it is used

 infer_call_result started recently to raise InferenceError for objects for which it
 could not find any returns. Previously it was silently raising a StopIteration,
 which was especially leaking when calling builtin methods.
 Since it is after all an inference method, it is expected that it
 could raise an InferenceError rather than returning nothing.

 Close PyCQA/pylint#2350

What's New in astroid 2.0.1?

Release Date: 2018-07-19

• Released to clear an old wheel package on PyPI

What's New in astroid 2.0?

Release Date: 2018-07-15

• String representation of nodes takes in account precedence and associativity rules of operators.

... (truncated)

Commits

• 5b5cd7a Prepare 2.0.4
• 3f7c4bc Make sure that assign nodes can find yield statements in their values
• 900a4b8 Release 2.0.3 with correct environment markers for pypy
• 5cc50ab Prepare 2.0.2
• f0044dd infer_call_result can raise InferenceError so make sure to handle that for th...
• 2894a1a Cut obsolete "explicit StopIteration" comments
• a48aa1e Use final Python 3.7 in Travis
• b8122df Spelling fixes
• ed835c5 Fix lint error
• 8d1de50 Add test for checking that a RuntimeError is no longer emitted in Python 3.7
• Additional commits viewable in compare view

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

---

Dependabot commands and options

You can trigger Dependabot actions by commenting on this PR:

• @dependabot rebase will rebase this PR
• @dependabot merge will merge this PR after your CI passes on it
• @dependabot reopen will reopen this PR if it is closed
• @dependabot ignore this [patch|minor|major] version will close this PR and stop Dependabot creating any more for this minor/major version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)
• @dependabot use these labels will set the current labels as the default for future PRs for this repo and language
• @dependabot use these reviewers will set the current reviewers as the default for future PRs for this repo and language
• @dependabot use these assignees will set the current assignees as the default for future PRs for this repo and language
• @dependabot use this milestone will set the current milestone as the default for future PRs for this repo and language
• @dependabot badge me will comment on this PR with code to add a "Dependabot enabled" badge to your readme

Additionally, you can set the following in your Dependabot dashboard:

• Update frequency (including time of day and day of week)
• Automerge options (never/patch/minor, and dev/runtime dependencies)
• Pull request limits (per update run and/or open at any time)
• Out-of-range updates (receive only lockfile updates, if desired)
• Security updates (receive only security updates, if desired)

Finally, you can contact us by mentioning @dependabot.

[dependabot-preview]

A newer version of astroid exists, but since this PR has been edited by someone other than Dependabot I haven't updated it. You'll get a PR for the updated version as normal once this PR is merged.