Can't parse unicode

[r-barnes]

I ask Pyre to type check a file including:

def foo(rhat=0.5, rtilde=0.2, μ=0.1, ν=0.1, T=8.0, P0=0.05, desired_dt=0.05):

and it returns

 ƛ Could not parse file at MirmiraniOster1978_single_season.py:3:30-3:30

It looks like it doesn't like the use of μ as a variable name, though that should be valid and Python 3.8.5 interprets it as such.

[JelleZijlstra]

Duplicate of #254 I think

[dkgi]

Will close in favor of the existing one. Our OCaml parser does not support unicode by default. We have plans to address this but they're not currently a priority :/