Try and provide more comprehensive __init__ error message if import fails

Author: rpep

fidimag/__init__.py

@@ -1,17 +1,42 @@
+import os
+import sys
 try:
     from . import extensions
+    from . import common
+    from . import atomistic
+    from . import micro
 except ImportError as e:
-    import os
     cwd = os.getcwd()
     FIDIMAG_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
     os.chdir(FIDIMAG_DIR)
-    print("Could not find fidimag extensions. Trying to build them now...")
+    message = """
+    Could not load the Fidimag extensions. This could be due to a few things:
+      1) The extensions are not built (we'll try and build them now).
+      2) FIDIMAG loads comon libraries dynamically. Currently, FIDIMAG requires
+         * Sundials 2.6.2
+         * FFTW 3.3.5
+         If you are using Linux, you may be able to download these through a
+         package manager such as apt or yum. However, convenience scripts
+         are provided in the folder bin to install these locally.
+      3) If you've run the scripts to install the dynamic libaries,
+         you may still need to export the LD_LIBRARY_PATH environment
+         variable. You can do this from the shell with:
+         export LD_LIBRARY_PATH={}:$LD_LIBRARY_PATH
+    """
+    print(message.format(FIDIMAG_DIR))
     os.system("make build")
     print("Building extensions done.")
     os.chdir(cwd)
-from . import common
-from . import atomistic
-from . import micro
+try:
+    from . import extensions
+    from . import common
+    from . import atomistic
+    from . import micro
+except ImportError as e:
+    raise ImportError("Loading the FIDIMAG extensions still didn't work."
+                      "\nTry the steps above!")
+
+
 from .gui import GUI
 
 citation = common.citation