FIX: Avoid excessive etelemetry calls

In cases where `check_latest_version` returned None, each time
`BaseInterface.__init__` was called would lead to another server ping.
This avoids this loop by falling to a string, n/a, if the server fails
to produce a version.

Author: mgxd

nipype/__init__.py

@@ -98,4 +98,4 @@ def check_latest_version(raise_exception=False):
         from .interfaces.base import BaseInterface
 
         if BaseInterface._etelemetry_version_data is None:
-            BaseInterface._etelemetry_version_data = check_latest_version()
+            BaseInterface._etelemetry_version_data = check_latest_version() or "n/a"

nipype/interfaces/base/core.py

@@ -186,7 +186,7 @@ def __init__(
             from ... import check_latest_version
 
             if BaseInterface._etelemetry_version_data is None:
-                BaseInterface._etelemetry_version_data = check_latest_version()
+                BaseInterface._etelemetry_version_data = check_latest_version() or "n/a"
 
         if not self.input_spec:
             raise Exception("No input_spec in class: %s" % self.__class__.__name__)