samを実行すると「UnixHTTPConnectionPool」が出て使えなくなったのを解消した

# こんな事象が発生した

あるプロダクトをcloneしてテスト実行しようと思ったら↓のようなエラーが発生した。

```
$ sam local invoke "${FUNC}" -e event.json
Traceback (most recent call last):
  File "/usr/local/Cellar/aws-sam-cli/0.15.0/libexec/lib/python3.7/site-packages/urllib3/connectionpool.py", line 384, in _make_request
    six.raise_from(e, None)
  File "<string>", line 2, in raise_from
  File "/usr/local/Cellar/aws-sam-cli/0.15.0/libexec/lib/python3.7/site-packages/urllib3/connectionpool.py", line 380, in _make_request
    httplib_response = conn.getresponse()
  File "/usr/local/opt/python/Frameworks/Python.framework/Versions/3.7/lib/python3.7/http/client.py", line 1321, in getresponse
    response.begin()
  File "/usr/local/opt/python/Frameworks/Python.framework/Versions/3.7/lib/python3.7/http/client.py", line 296, in begin
    version, status, reason = self._read_status()
  File "/usr/local/opt/python/Frameworks/Python.framework/Versions/3.7/lib/python3.7/http/client.py", line 257, in _read_status
    line = str(self.fp.readline(_MAXLINE + 1), "iso-8859-1")
  File "/usr/local/opt/python/Frameworks/Python.framework/Versions/3.7/lib/python3.7/socket.py", line 589, in readinto
    return self._sock.recv_into(b)
socket.timeout: timed out

During handling of the above exception, another exception occurred:

~ 省略 ~

  File "/usr/local/Cellar/aws-sam-cli/0.15.0/libexec/lib/python3.7/site-packages/docker/api/client.py", line 230, in _get
    return self.get(url, **self._set_request_timeout(kwargs))
  File "/usr/local/Cellar/aws-sam-cli/0.15.0/libexec/lib/python3.7/site-packages/requests/sessions.py", line 546, in get
    return self.request('GET', url, **kwargs)
  File "/usr/local/Cellar/aws-sam-cli/0.15.0/libexec/lib/python3.7/site-packages/requests/sessions.py", line 533, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/local/Cellar/aws-sam-cli/0.15.0/libexec/lib/python3.7/site-packages/requests/sessions.py", line 646, in send
    r = adapter.send(request, **kwargs)
  File "/usr/local/Cellar/aws-sam-cli/0.15.0/libexec/lib/python3.7/site-packages/requests/adapters.py", line 529, in send
    raise ReadTimeout(e, request=request)
requests.exceptions.ReadTimeout: UnixHTTPConnectionPool(host='localhost', port=None): Read timed out. (read timeout=60)
```

ちなみに環境はこんな感じ

```
$ sam --version
SAM CLI, version 0.15.0

$ python -V
Python 3.7.0

$ docker -v
Docker version 18.09.2, build 6247962
```

# 何ぞこれ？

→　docker がおかしくなると起きる現象のよう


# 解決策

docker をrestartしたら動くようになった

```
$ sam local invoke "${FUNC}" -e event.json
2019-05-08 18:55:04 Found credentials in shared credentials file: ~/.aws/credentials
2019-05-08 18:55:04 Invoking hello-world (go1.x)

Fetching lambci/lambda:go1.x Docker container image....................................................................................................................................................................................................     ..................................................................................................
2019-05-08 18:55:40 Mounting /workspace/hello-world as /var/task:ro,delegated inside runtime container
START RequestId: 74e4d6a4-3f61-1dcb-c4bd-f8ec32da4504 Version: $LATEST
[SUCCESS] event doing!! - ObjectCreated:Put 
[aws:s3 - 1970-01-01 00:00:00 +0000 UTC] Bucket = test.secondly, Key = app/test.json 
END RequestId: 74e4d6a4-3f61-1dcb-c4bd-f8ec32da4504
REPORT RequestId: 74e4d6a4-3f61-1dcb-c4bd-f8ec32da4504  Duration: 4.49 ms       Billed Duration: 100 ms   Memory Size: 128 MB     Max Memory Used: 6 MB
null
```