Bug 1556707

Description of problem:
Found this indirectly through TurboGears test suite (it FTBFS, bug 1555584) which uses turbocheetah which calls Compiler.Compiler():

Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/CherryPy-2.3.0-py2.7.egg/cherrypy/_cphttptools.py", line 121, in _run
    self.main()
  File "/usr/lib/python2.7/site-packages/CherryPy-2.3.0-py2.7.egg/cherrypy/_cphttptools.py", line 264, in main
    body = page_handler(*virtual_path, **self.params)
  File "<string>", line 3, in with_json_via_accept
  File "/builddir/build/BUILD/TurboGears-1.1.3/turbogears/controllers.py", line 384, in <lambda>
    expose = lambda func, *args, **kw: func(*args, **kw)
  File "<string>", line 3, in with_json_via_accept
  File "/builddir/build/BUILD/TurboGears-1.1.3/turbogears/controllers.py", line 384, in <lambda>
    expose = lambda func, *args, **kw: func(*args, **kw)
  File "<string>", line 3, in with_json_via_accept
  File "/builddir/build/BUILD/TurboGears-1.1.3/turbogears/controllers.py", line 361, in expose
    *args, **kw)
  File "<generated code>", line 0, in run_with_transaction
  File "/usr/lib/python2.7/site-packages/peak/rules/core.py", line 153, in __call__
    return self.body(*args, **kw)
  File "/builddir/build/BUILD/TurboGears-1.1.3/turbogears/database.py", line 458, in sa_rwt
    retval = func(*args, **kw)
  File "<generated code>", line 0, in _expose
  File "/usr/lib/python2.7/site-packages/peak/rules/core.py", line 153, in __call__
    return self.body(*args, **kw)
  File "/builddir/build/BUILD/TurboGears-1.1.3/turbogears/controllers.py", line 390, in <lambda>
    fragment, options, args, kw)))
  File "/builddir/build/BUILD/TurboGears-1.1.3/turbogears/controllers.py", line 451, in _execute_func
    fragment, **options)
  File "/builddir/build/BUILD/TurboGears-1.1.3/turbogears/controllers.py", line 100, in _process_output
    headers=headers, fragment=fragment, **options)
  File "/builddir/build/BUILD/TurboGears-1.1.3/turbogears/view/base.py", line 203, in render
    return engine.render(**kw)
  File "/usr/lib/python2.7/site-packages/turbocheetah/cheetahsupport.py", line 103, in render
    tempclass = self.load_template(template)
  File "/usr/lib/python2.7/site-packages/turbocheetah/cheetahsupport.py", line 83, in load_template
    mod = _compile_template(package, basename, tfile)
  File "/usr/lib/python2.7/site-packages/turbocheetah/cheetahsupport.py", line 16, in _compile_template
    code = str(Compiler.Compiler(file=tfile, mainClassName=basename))
  File "/usr/lib64/python2.7/site-packages/Cheetah/Compiler.py", line 1544, in __init__
    encoding = settings.get('encoding')
AttributeError: 'NoneType' object has no attribute 'get'

Version-Release number of selected component (if applicable):
python2-cheetah-3.0.0-20.fc29.x86_64

How reproducible:
easily

Steps to Reproduce:
1. python -c "import Cheetah.Compiler; Cheetah.Compiler.Compiler(file='/dev/null')"

Actual results:
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib64/python2.7/site-packages/Cheetah/Compiler.py", line 1544, in __init__
    encoding = settings.get('encoding')
AttributeError: 'NoneType' object has no attribute 'get'

Expected results:
/usr/lib64/python2.7/site-packages/Cheetah/Compiler.py:1555: UserWarning: You supplied an empty string for the source!
  warnings.warn("You supplied an empty string for the source!", )

Additional info:
Seems to have regressed in 3.0.0 in this commit:
https://github.com/CheetahTemplate3/cheetah3/commit/1f3e4ed66a343f21f6171e42b7222b5189a1fdce
and then fixed in this commit in 3.0.1:
https://github.com/CheetahTemplate3/cheetah3/commit/050bb8a8cfd002e5b811e1864b5d41fee6a1591e