add installation instructions

Author: PythonFZ

ipsuite/calculators/cp2k.py

@@ -22,7 +22,15 @@
 import znh5md
 import zntrack
 from ase.calculators.singlepoint import SinglePointCalculator
-from cp2k_input_tools.generator import CP2KInputGenerator
+
+try:
+    from cp2k_input_tools.generator import CP2KInputGenerator
+except ImportError as err:
+    raise ImportError(
+        "Please install the newest development version of cp2k-input-tools: 'pip install"
+        " git+https://github.com/cp2k/cp2k-input-tools.git'"
+    ) from err
+
 
 from ipsuite import base