我在Raspberry Pi上安装numpy时遇到此问题（Python 3.6.6，而没有anaconda）：
pi@raspberrypi:~/Desktop$ sudo pip3 install numpy
pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available.
Collecting numpy
Could not fetch URL https://pypi.python.org/simple/numpy/: There was a problem confirming the ssl certificate: Can't connect to HTTPS URL because the SSL module is not available. - skipping
Could not find a version that satisfies the requirement numpy (from versions: )
No matching distribution found for numpy
出了什么问题，我该如何解决？