1. Steps

$ pip install notebook
DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support
Requirement already satisfied: notebook in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (5.7.10)
Requirement already satisfied: jupyter-client>=5.2.0 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (5.3.4)
Requirement already satisfied: nbformat in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (4.4.0)
Requirement already satisfied: ipython-genutils in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (0.2.0)
Requirement already satisfied: terminado>=0.8.1 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (0.8.3)
Requirement already satisfied: prometheus-client in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (0.11.0)
Requirement already satisfied: Send2Trash in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (1.8.0)
Requirement already satisfied: pyzmq>=17 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (18.1.0)
Requirement already satisfied: jinja2 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (2.11.3)
Requirement already satisfied: ipaddress; python_version == "2.7" in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (1.0.23)
Requirement already satisfied: tornado<7,>=4.1 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (5.1.1)
Requirement already satisfied: traitlets>=4.2.1 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (4.3.3)
Requirement already satisfied: ipykernel in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (4.6.1)
Requirement already satisfied: nbconvert<6.0 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (5.6.1)
Requirement already satisfied: jupyter-core>=4.4.0 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (4.6.1)
Requirement already satisfied: python-dateutil>=2.1 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from jupyter-client>=5.2.0->notebook) (2.8.2)
Requirement already satisfied: jsonschema!=2.5.0,>=2.4 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from nbformat->notebook) (2.6.0)
Requirement already satisfied: MarkupSafe>=0.23 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from jinja2->notebook) (1.1.1)
Requirement already satisfied: futures in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from tornado<7,>=4.1->notebook) (3.3.0)
Requirement already satisfied: singledispatch in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from tornado<7,>=4.1->notebook) (3.7.0)
Requirement already satisfied: backports_abc>=0.4 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from tornado<7,>=4.1->notebook) (0.5)
Requirement already satisfied: enum34; python_version == "2.7" in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from traitlets>=4.2.1->notebook) (1.1.6)
Requirement already satisfied: six in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from traitlets>=4.2.1->notebook) (1.16.0)
Requirement already satisfied: decorator in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from traitlets>=4.2.1->notebook) (5.1.0)
ERROR: Package 'decorator' requires a different Python: 2.7.18 not in '>=3.5'

$ pip install decorator==?
DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support
ERROR: Could not find a version that satisfies the requirement decorator==? (from versions: 3.3.1, 3.3.2, 3.3.3, 3.4.0, 3.4.2, 4.0.0, 4.0.1, 4.0.2, 4.0.3, 4.0.4, 4.0.6, 4.0.8, 4.0.9, 4.0.10, 4.0.11, 4.1.0, 4.1.1, 4.1.2, 4.2.1, 4.3.0, 4.3.1, 4.3.2, 4.4.0, 4.4.1, 4.4.2)
ERROR: No matching distribution found for decorator==?

$ pip install decorator==4.4.2
DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support
Collecting decorator==4.4.2
  WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7f685a8e9d90>: Failed to establish a new connection: [Errno 101] Network is unreachable',)': /packages/ed/1b/72a1821152d07cf1d8b6fce298aeb06a7eb90f4d6d41acec9861e7cc6df0/decorator-4.4.2-py2.py3-none-any.whl
  WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7f685a996650>: Failed to establish a new connection: [Errno 101] Network is unreachable',)': /packages/ed/1b/72a1821152d07cf1d8b6fce298aeb06a7eb90f4d6d41acec9861e7cc6df0/decorator-4.4.2-py2.py3-none-any.whl
  WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7f685a87e050>: Failed to establish a new connection: [Errno 101] Network is unreachable',)': /packages/ed/1b/72a1821152d07cf1d8b6fce298aeb06a7eb90f4d6d41acec9861e7cc6df0/decorator-4.4.2-py2.py3-none-any.whl
  Downloading https://files.pythonhosted.org/packages/ed/1b/72a1821152d07cf1d8b6fce298aeb06a7eb90f4d6d41acec9861e7cc6df0/decorator-4.4.2-py2.py3-none-any.whl
Installing collected packages: decorator
  Found existing installation: decorator 5.1.0
    Uninstalling decorator-5.1.0:
      Successfully uninstalled decorator-5.1.0
Successfully installed decorator-4.4.2

$ pip install notebook
DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support
Requirement already satisfied: notebook in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (5.7.10)
Requirement already satisfied: jupyter-client>=5.2.0 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (5.3.4)
Requirement already satisfied: nbformat in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (4.4.0)
Requirement already satisfied: ipython-genutils in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (0.2.0)
Requirement already satisfied: terminado>=0.8.1 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (0.8.3)
Requirement already satisfied: Send2Trash in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (1.8.0)
Requirement already satisfied: pyzmq>=17 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (18.1.0)
Requirement already satisfied: prometheus-client in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (0.11.0)
Requirement already satisfied: jinja2 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (2.11.3)
Requirement already satisfied: ipaddress; python_version == "2.7" in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (1.0.23)
Requirement already satisfied: tornado<7,>=4.1 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (5.1.1)
Requirement already satisfied: traitlets>=4.2.1 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (4.3.3)
Requirement already satisfied: ipykernel in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (4.6.1)
Requirement already satisfied: nbconvert<6.0 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (5.6.1)
Requirement already satisfied: jupyter-core>=4.4.0 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from notebook) (4.6.1)
Requirement already satisfied: python-dateutil>=2.1 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from jupyter-client>=5.2.0->notebook) (2.8.2)
Requirement already satisfied: jsonschema!=2.5.0,>=2.4 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from nbformat->notebook) (2.6.0)
Requirement already satisfied: MarkupSafe>=0.23 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from jinja2->notebook) (1.1.1)
Requirement already satisfied: futures in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from tornado<7,>=4.1->notebook) (3.3.0)
Requirement already satisfied: singledispatch in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from tornado<7,>=4.1->notebook) (3.7.0)
Requirement already satisfied: backports_abc>=0.4 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from tornado<7,>=4.1->notebook) (0.5)
Requirement already satisfied: enum34; python_version == "2.7" in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from traitlets>=4.2.1->notebook) (1.1.6)
Requirement already satisfied: six in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from traitlets>=4.2.1->notebook) (1.16.0)
Requirement already satisfied: decorator in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from traitlets>=4.2.1->notebook) (4.4.2)
Requirement already satisfied: entrypoints>=0.2.2 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from nbconvert<6.0->notebook) (0.3)
Requirement already satisfied: testpath in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from nbconvert<6.0->notebook) (0.4.4)
Requirement already satisfied: pygments in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from nbconvert<6.0->notebook) (2.5.2)
Requirement already satisfied: bleach in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from nbconvert<6.0->notebook) (3.3.1)
Requirement already satisfied: pandocfilters>=1.4.1 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from nbconvert<6.0->notebook) (1.4.2)
Requirement already satisfied: mistune<2,>=0.8.1 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from nbconvert<6.0->notebook) (0.8.4)
Requirement already satisfied: defusedxml in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from nbconvert<6.0->notebook) (0.7.1)
Requirement already satisfied: functools32 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from jsonschema!=2.5.0,>=2.4->nbformat->notebook) (3.2.3.post2)
Requirement already satisfied: webencodings in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from bleach->nbconvert<6.0->notebook) (0.5.1)
Requirement already satisfied: packaging in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from bleach->nbconvert<6.0->notebook) (20.9)
Requirement already satisfied: pyparsing>=2.0.2 in ./anaconda3/envs/python2.7/lib/python2.7/site-packages (from packaging->bleach->nbconvert<6.0->notebook) (2.4.7)