Python 3.7 (#2067)

Author: slozier

Directory.Build.props

@@ -29,6 +29,7 @@
 
     <PythonSymbols>PYTHON_$(MajorVersion)$(MinorVersion)</PythonSymbols>
     <PythonSymbols Condition="'$(MajorVersion)$(MinorVersion)' >= '36'">$(PythonSymbols);PYTHON_36_OR_GREATER</PythonSymbols>
+    <PythonSymbols Condition="'$(MajorVersion)$(MinorVersion)' >= '37'">$(PythonSymbols);PYTHON_37_OR_GREATER</PythonSymbols>
 
     <GenerateAssemblyTitleAttribute>false</GenerateAssemblyTitleAttribute>
 

src/core/IronPython/Runtime/PythonContext.cs

@@ -303,6 +303,9 @@ void BootstrapImportLib() {
                     LoadModuleFromResource("_frozen_importlib_external", "IronPython.Modules._bootstrap_external.py");
 #endif
                     PythonOps.Invoke(SharedClsContext, _frozen_importlib, "_install", SystemState, GetBuiltinModule("_imp"));
+#if PYTHON_37_OR_GREATER
+                    PythonOps.Invoke(SharedClsContext, _frozen_importlib, "_install_external_importers");
+#endif
                 } catch { }
 
                 PythonModule LoadModuleFromResource(string name, string resourceName) {