[core] checkTemplateVersions: Ensure nodes are not loaded several times

By performing a `initNodes()` every single time `checkTemplateVersions`
was called without ever unregistering the nodes, warnings about nodes
being already registered were raised when for example calling
`checkAllTemplatesVersions`.

meshroom/core/test.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 # coding:utf-8
 
-from meshroom.core import pipelineTemplates, Version
+from meshroom.core import unregisterNodeType, pipelineTemplates, Version
 from meshroom.core.node import CompatibilityIssue, CompatibilityNode
 from meshroom.core.graphIO import GraphIO
 
@@ -9,13 +9,15 @@ import meshroom
 
 import json
 
-def checkTemplateVersions(path: str) -> bool:
+def checkTemplateVersions(path: str, nodesAlreadyLoaded: bool = False) -> bool:
     """ Check whether there is a compatibility issue with the nodes saved in the template provided with "path". """
+    if not nodesAlreadyLoaded:
         meshroom.core.initNodes()
 
     with open(path) as jsonFile:
         fileData = json.load(jsonFile)
 
+    try:
         graphData = fileData.get(GraphIO.Keys.Graph, fileData)
         if not isinstance(graphData, dict):
             return False
@@ -57,12 +59,19 @@ def checkTemplateVersions(path: str) -> bool:
 
         return True
 
+    finally:
+        if not nodesAlreadyLoaded:
+            nodeTypes = [nodeType for _, nodeType in meshroom.core.nodesDesc.items()]
+            for nodeType in nodeTypes:
+                unregisterNodeType(nodeType)
+
 
 def checkAllTemplatesVersions() -> bool:
+    meshroom.core.initNodes()
     meshroom.core.initPipelines()
 
     validVersions = []
     for _, path in pipelineTemplates.items():
-        validVersions.append(checkTemplateVersions(path))
+        validVersions.append(checkTemplateVersions(path, nodesAlreadyLoaded=True))
 
     return all(validVersions)