added warnings for non-required (not present in requirements.txt) packages in io.py and ipysliderule.py

Author: jpswinski

sliderule/io.py

@@ -27,13 +27,19 @@
 # OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 # ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+import sys
 import warnings
 import datetime
-import scipy.io
 import geopandas
-import h5py
 import numpy as np
 
+# imports with warnings if not present
+try:
+    import scipy.io
+    import h5py
+except ModuleNotFoundError as e:
+    sys.stderr.write("Warning: missing packages, some functions will throw an exception if called. (%s)\n" % (str(e)))
+
 # attributes for ATL06-SR variables
 def get_attributes(**kwargs):
     # set default keyword arguments

sliderule/ipysliderule.py

@@ -28,16 +28,28 @@
 # ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 import os
+import sys
 import copy
 import datetime
-import ipywidgets
-import ipyleaflet
 import numpy as np
 from traitlets.utils.bunch import Bunch
-import tkinter.filedialog
-import IPython.display
 import sliderule.io
 
+# imports with warnings if not present
+try:
+    import ipywidgets
+    import tkinter.filedialog
+    import IPython.display
+except ModuleNotFoundError as e:
+    sys.stderr.write("Warning: missing packages, some functions will throw an exception if called. (%s)\n" % (str(e)))
+
+# imports that raise error if not present
+try:
+    import ipyleaflet
+except ModuleNotFoundError as e:
+    sys.stderr.write("Error: missing required packages. (%s)\n" % (str(e)))
+    raise
+
 class widgets:
     def __init__(self):
         # dropdown menu for setting asset