Currently you need to explicitly add it to PATH if not already done. This was the error for me.
Ideally it should work out of the box like InstaPy.

Traceback (most recent call last):
File "classify_profiles.py", line 21, in
browser = webdriver.Chrome('./assets/chromedriver', chrome_options=chrome_options)
File "/Users/ishandutta2007/.pyenv/versions/3.6.0/lib/python3.6/site-packages/selenium/webdriver/chrome/webdriver.py", line 73, in init
self.service.start()
File "/Users/ishandutta2007/.pyenv/versions/3.6.0/lib/python3.6/site-packages/selenium/webdriver/common/service.py", line 83, in start
os.path.basename(self.path), self.start_error_message)
selenium.common.exceptions.WebDriverException: Message: 'chromedriver' executable needs to be in PATH. Please see https://sites.google.com/a/chromium.org/chromedriver/home

pi@raspberrypi:~/InstaPy $ python3.7 quickstart.py

.. .. .. .. .. .. .. ..
Workspace in use: "/home/pi/InstaPy"

OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
INFO [2019-04-13 22:13:33] ['''''''''''] Session started!
oooooooooooooooooooooooooooooooooooooooooooooooooooooo

Cookie file not found, creating cookie...

INFO [2019-04-13 22:13:39] [''''''''''] Sessional Live Report:
|> No any statistics to show

[Session lasted 11.22 seconds]

OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
INFO [2019-04-13 22:13:39] ['''''''''''] Session ended!
ooooooooooooooooooooooooooooooooooooooooooooooooooooo

Traceback (most recent call last):
File "/usr/local/lib/python3.7/site-packages/urllib3/connectionpool.py", line 600, in urlopen
chunked=chunked)
File "/usr/local/lib/python3.7/site-packages/urllib3/connectionpool.py", line 384, in _make_request
six.raise_from(e, None)
File "", line 2, in raise_from
File "/usr/local/lib/python3.7/site-packages/urllib3/connectionpool.py", line 380, in _make_request
httplib_response = conn.getresponse()
File "/usr/local/lib/python3.7/http/client.py", line 1321, in getresponse
response.begin()
File "/usr/local/lib/python3.7/http/client.py", line 296, in begin
version, status, reason = self._read_status()
File "/usr/local/lib/python3.7/http/client.py", line 265, in _read_status
raise RemoteDisconnected("Remote end closed connection without"
http.client.RemoteDisconnected: Remote end closed connection without response

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "quickstart.py", line 20, in
with smart_run(session):
File "/usr/local/lib/python3.7/contextlib.py", line 112, in enter
return next(self.gen)
File "/home/pi/.local/lib/python3.7/site-packages/instapy/util.py", line 1683, in smart_run
session.login()
File "/home/pi/.local/lib/python3.7/site-packages/instapy/instapy.py", line 393, in login
self.bypass_with_mobile):
File "/home/pi/.local/lib/python3.7/site-packages/instapy/login_util.py", line 173, in login_user
reload_webpage(browser)
File "/home/pi/.local/lib/python3.7/site-packages/instapy/util.py", line 1710, in reload_webpage
browser.execute_script("location.reload()")
File "/home/pi/.local/lib/python3.7/site-packages/selenium/webdriver/remote/webdriver.py", line 636, in execute_script
'args': converted_args})['value']
File "/home/pi/.local/lib/python3.7/site-packages/selenium/webdriver/remote/webdriver.py", line 319, in execute
response = self.command_executor.execute(driver_command, params)
File "/home/pi/.local/lib/python3.7/site-packages/selenium/webdriver/remote/remote_connection.py", line 374, in execute
return self._request(command_info[0], url, body=data)
File "/home/pi/.local/lib/python3.7/site-packages/selenium/webdriver/remote/remote_connection.py", line 397, in _request
resp = self._conn.request(method, url, body=body, headers=headers)
File "/usr/local/lib/python3.7/site-packages/urllib3/request.py", line 72, in request
**urlopen_kw)
File "/usr/local/lib/python3.7/site-packages/urllib3/request.py", line 150, in request_encode_body
return self.urlopen(method, url, **extra_kw)
File "/usr/local/lib/python3.7/site-packages/urllib3/poolmanager.py", line 323, in urlopen
response = conn.urlopen(method, u.request_uri, **kw)
File "/usr/local/lib/python3.7/site-packages/urllib3/connectionpool.py", line 638, in urlopen
_stacktrace=sys.exc_info()[2])
File "/usr/local/lib/python3.7/site-packages/urllib3/util/retry.py", line 367, in increment
raise six.reraise(type(error), error, _stacktrace)
File "/usr/local/lib/python3.7/site-packages/urllib3/packages/six.py", line 685, in reraise
raise value.with_traceback(tb)
File "/usr/local/lib/python3.7/site-packages/urllib3/connectionpool.py", line 600, in urlopen
chunked=chunked)
File "/usr/local/lib/python3.7/site-packages/urllib3/connectionpool.py", line 384, in _make_request
six.raise_from(e, None)
File "", line 2, in raise_from
File "/usr/local/lib/python3.7/site-packages/urllib3/connectionpool.py", line 380, in _make_request
httplib_response = conn.getresponse()
File "/usr/local/lib/python3.7/http/client.py", line 1321, in getresponse
response.begin()
File "/usr/local/lib/python3.7/http/client.py", line 296, in begin
version, status, reason = self._read_status()
File "/usr/local/lib/python3.7/http/client.py", line 265, in _read_status
raise RemoteDisconnected("Remote end closed connection without"
urllib3.exceptions.ProtocolError: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))
pi@raspberrypi:~/InstaPy $