making nd2 and scanimage-tiff-reader optional (#950)

Author: carsen-stringer

suite2p/io/nd2.py

@@ -4,8 +4,12 @@
 import time
 import numpy as np
 from . import utils
-import nd2
 
+try:
+    import nd2 
+    ND2 = True
+except ImportError:
+    ND2 = False
 
 def nd2_to_binary(ops):
     """finds nd2 files and writes them to binaries

suite2p/io/tiff.py

@@ -15,6 +15,7 @@
     from ScanImageTiffReader import ScanImageTiffReader
     HAS_SCANIMAGE = True
 except ImportError:
+    ScanImageTiffReader = None
     HAS_SCANIMAGE = False
 
 
@@ -106,6 +107,7 @@ def use_sktiff_reader(tiff_filename, batch_size: Optional[int] = None) -> bool:
             return True
     else:
         print("NOTE: ScanImageTiffReader not installed, using tifffile")
+        return True
 
 
 def tiff_to_binary(ops):