Update test/python/pythoncall.jl

Author: ChrisRackauckas

test/python/pythoncall.jl

@@ -1,11 +1,11 @@
 using DifferentialEquations, PythonCall
 
-py""" # This is a mess because normal site-packages is not writeable in CI
+pyexec(""" # This is a mess because normal site-packages is not writeable in CI
 import subprocess, sys, site
 subprocess.run([sys.executable, '-m', 'pip', 'install', '--user', 'julia'])
 subprocess.run([sys.executable, '-m', 'pip', 'install', '--user', 'diffeqpy'])
 sys.path.append(site.getusersitepackages())
-"""
+""")
 
 @testset "Use of DifferentialEquations through PythonCall with user code written in Python" begin
     pyexec("""