support latest PythonCall (fixes #1)

Author: stevengj

Project.toml

@@ -12,7 +12,7 @@ Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 VersionParsing = "81def892-9a0e-5fdd-b105-ffc91e053289"
 
 [compat]
-PythonCall = "0.5"
+PythonCall = "0.5, 0.6, 0.7, 0.8"
 CondaPkg = "0.2"
 julia = "1.4"
 LaTeXStrings = "1"