avoid calling private method in subclasses of KernelSpecManager

on the result of a public overrideable method,
which breaks subclasses that don't override get_all_specs

Author: minrk

jupyter_client/kernelspec.py

@@ -254,7 +254,14 @@ def get_all_specs(self):
         res = {}
         for kname, resource_dir in d.items():
             try:
-                spec = self._get_kernel_spec_by_name(kname, resource_dir)
+                if self.__class__ is KernelSpecManager:
+                    spec = self._get_kernel_spec_by_name(kname, resource_dir)
+                else:
+                    # avoid calling private methods in subclasses,
+                    # which may have overridden find_kernel_specs
+                    # and get_kernel_spec, but not the newer get_all_specs
+                    spec = self.get_kernel_spec(kname)
+
                 res[kname] = {
                     "resource_dir": resource_dir,
                     "spec": spec.to_dict()