RaspberryPi3 Bで OpenCVをインストールしたいです

Question

前提・実現したいこと

RaspberryPi3 Bで OpenCVをインストールしたいです。
OSはRaspbian Stretchを使用してます。
下のサイトを参考にしています。
https://www.pyimagesearch.com/2017/09/04/raspbian-stretch-install-opencv-3-python-on-your-raspberry-pi/

発生している問題・エラーメッセージ

Step #4: Python 2.7 or Python 3?
にて問題が生じました。　解決方法をよろしくお願いします。

pi@raspberrypi:~ $  sudo python get-pip.py
Looking in indexes: https://pypi.org/simple, https://www.piwheels.org/simple
Collecting pip
  Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)': /simple/pip/
  Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)': /simple/pip/
  Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)': /simple/pip/
  Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)': /simple/pip/
  Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)': /simple/pip/
  Could not fetch URL https://pypi.org/simple/pip/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/pip/ (Caused by SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)) - skipping
  Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)': /simple/pip/
  Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)': /simple/pip/
  Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)': /simple/pip/
  Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)': /simple/pip/
  Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)': /simple/pip/
  Could not fetch URL https://www.piwheels.org/simple/pip/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='www.piwheels.org', port=443): Max retries exceeded with url: /simple/pip/ (Caused by SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)) - skipping
  Could not find a version that satisfies the requirement pip (from versions: )
No matching distribution found for pip
Could not fetch URL https://pypi.org/simple/pip/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/pip/ (Caused by SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)) - skipping
Could not fetch URL https://www.piwheels.org/simple/pip/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='www.piwheels.org', port=443): Max retries exceeded with url: /simple/pip/ (Caused by SSLError(SSLError("bad handshake: SysCallError(104, 'ECONNRESET')",),)) - skipping

エラーメッセージ

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ソースコード

試したこと

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補足情報（FW/ツールのバージョンなど）

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