`merge_xml_files` does not work above python3.9

[kvslab]

`merge_xml_files` does not work above python3.9

[keiyamamo]

Right now, environment.yml specifies python version to be 3.10, but I do not know if we need python 3.10.
We can downgrade python version to, for example, 3.8 and change the documentation to say that turtle works with python<3.9 instead of updating this function.

turtleFSI/environment.yml

Line 7 in b4df373

- python=3.10

What do you think, @johannesring @jorgensd ?

[jorgensd]

Right now, environment.yml specifies python version to be 3.10, but I do not know if we need python 3.10. We can downgrade python version to, for example, 3.8 and change the documentation to say that turtle works with python<3.9 instead of updating this function.

turtleFSI/environment.yml

Line 7 in b4df373

- python=3.10

What do you think, @johannesring @jorgensd ?

Python 3.7 is EOL (end of life) in June, so I wouldn't bother supporting it.
However, we should support Python3.8.
Thus I've made #47 that only enforces a min bound on the python env, and we can test it with anaconda.

[johannesring]

I ran into the same problem in Oasis not long ago and fixed it by using list(element) instead of element.getchildren() as written in the documentation. For turtleFSI this would be:

--- a/turtleFSI/problems/__init__.py
+++ b/turtleFSI/problems/__init__.py
@@ -419,14 +419,14 @@ def merge_xml_files(files):
     # Get last timestep of first tree
     base_tree = trees[indexes[0]]
     last_node = base_tree.getroot()[0][0][-1]
-    ind = 1 if len(last_node.getchildren()) == 3 else 2
+    ind = 1 if len(list(last_node)) == 3 else 2
     last_timestep = float(last_node[ind].attrib["Value"])
 
     # Append
     for index in indexes[1:]:
         tree = trees[index]
-        for node in tree.getroot()[0][0].getchildren():
-            ind = 1 if len(node.getchildren()) == 3 else 2
+        for node in list(tree.getroot()[0][0]):
+            ind = 1 if len(list(node)) == 3 else 2
             if last_timestep < float(node[ind].attrib["Value"]):
                 base_tree.getroot()[0][0].append(node)
                 last_timestep = float(node[ind].attrib["Value"])

[keiyamamo]

solved #50