ModuleNotFoundError: No module named 'lunarcalendar'

I hit ` ModuleNotFoundError: No module named 'lunarcalendar'` when installing prophet.

```
Building wheels for collected packages: prophet
Building wheel for prophet (setup.py): started
Building wheel for prophet (setup.py): finished with status 'error'
ERROR: Command errored out with exit status 1:
command: /usr/local/bin/python -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-q1x_o3cd/prophet_ba1f04c038ba4ede95d8ab29b0d56834/setup.py'"'"'; __file__='"'"'/tmp/pip-install-q1x_o3cd/prophet_ba1f04c038ba4ede95d8ab29b0d56834/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' bdist_wheel -d /tmp/pip-wheel-_r9iav0t
cwd: /tmp/pip-install-q1x_o3cd/prophet_ba1f04c038ba4ede95d8ab29b0d56834/
Complete output (44 lines):
running bdist_wheel
running build
running build_py
creating build
creating build/lib
creating build/lib/prophet
creating build/lib/prophet/stan_model
Traceback (most recent call last):
File "", line 1, in
File "/tmp/pip-install-q1x_o3cd/prophet_ba1f04c038ba4ede95d8ab29b0d56834/setup.py", line 150, in
long_description_content_type='text/markdown',
File "/usr/local/lib/python3.7/site-packages/setuptools/__init__.py", line 153, in setup
return distutils.core.setup(**attrs)
File "/usr/local/lib/python3.7/distutils/core.py", line 148, in setup
dist.run_commands()
File "/usr/local/lib/python3.7/distutils/dist.py", line 966, in run_commands
self.run_command(cmd)
File "/usr/local/lib/python3.7/distutils/dist.py", line 985, in run_command
cmd_obj.run()
File "/usr/local/lib/python3.7/site-packages/wheel/bdist_wheel.py", line 299, in run
self.run_command('build')
File "/usr/local/lib/python3.7/distutils/cmd.py", line 313, in run_command
self.distribution.run_command(command)
File "/usr/local/lib/python3.7/distutils/dist.py", line 985, in run_command
cmd_obj.run()
File "/usr/local/lib/python3.7/distutils/command/build.py", line 135, in run
self.run_command(cmd_name)
File "/usr/local/lib/python3.7/distutils/cmd.py", line 313, in run_command
self.distribution.run_command(command)
File "/usr/local/lib/python3.7/distutils/dist.py", line 985, in run_command
cmd_obj.run()
File "/tmp/pip-install-q1x_o3cd/prophet_ba1f04c038ba4ede95d8ab29b0d56834/setup.py", line 48, in run
build_models(target_dir)
File "/tmp/pip-install-q1x_o3cd/prophet_ba1f04c038ba4ede95d8ab29b0d56834/setup.py", line 36, in build_models
from prophet.models import StanBackendEnum
File "/tmp/pip-install-q1x_o3cd/prophet_ba1f04c038ba4ede95d8ab29b0d56834/prophet/__init__.py", line 8, in
from prophet.forecaster import Prophet
File "/tmp/pip-install-q1x_o3cd/prophet_ba1f04c038ba4ede95d8ab29b0d56834/prophet/forecaster.py", line 17, in
from prophet.make_holidays import get_holiday_names, make_holidays_df
File "/tmp/pip-install-q1x_o3cd/prophet_ba1f04c038ba4ede95d8ab29b0d56834/prophet/make_holidays.py", line 14, in
import prophet.hdays as hdays_part2
File "/tmp/pip-install-q1x_o3cd/prophet_ba1f04c038ba4ede95d8ab29b0d56834/prophet/hdays.py", line 14, in
from lunarcalendar import Lunar, Converter
ModuleNotFoundError: No module named 'lunarcalendar'
----------------------------------------
ERROR: Failed building wheel for prophet
```