display matplotlib backend as part of sys-info

Author: mscheltienne

template/utils/_config.py

@@ -91,4 +91,16 @@ def _list_dependencies_info(
             version_ = version(dep)
         except Exception:
             version_ = "Not found."
-        out(f"{dep}:".ljust(ljust) + version_ + "\n")
+
+        # handle special dependencies with backends, C dep, ..
+        if dep in ("matplotlib", "seaborn") and version_ != "Not found.":
+            try:
+                from matplotlib import pyplot as plt
+                backend = plt.get_backend()
+            except Exception:
+                backend = "Not found"
+
+            out(f"{dep}:".ljust(ljust) + version_ + f" (backend: {backend})\n")
+
+        else:
+            out(f"{dep}:".ljust(ljust) + version_ + "\n")