backend: Error handling

pywal/backends/colorthief.py

@@ -3,7 +3,13 @@ Generate a colorscheme using ColorThief.
 """
 import sys
 
-from colorthief import ColorThief
+try:
+    from colorthief import ColorThief
+
+except ImportError:
+    print("Error: ColorThief wasn't found on your system.",
+          "Try another backend. (wal --backend)")
+    sys.exit(1)
 
 from .. import util
 

pywal/backends/colorz.py

@@ -1,7 +1,9 @@
 """
 Generate a colorscheme using Colorz.
 """
+import shutil
 import subprocess
+import sys
 
 from .. import util
 
@@ -40,6 +42,11 @@ def adjust(colors, light):
 
 def get(img, light=False):
     """Get colorscheme."""
+    if not shutil.which("colorz"):
+        print("Error: Colorz wasn't found on your system.",
+              "Try another backend. (wal --backend)")
+        sys.exit(1)
+
     colors = gen_colors(img)
     colors = [color.decode('UTF-8').split()[0] for color in colors]
     return adjust(colors, light)

pywal/backends/wal.py

@@ -26,8 +26,8 @@ def has_im():
     elif shutil.which("convert"):
         return ["convert"]
 
-    print("error: imagemagick not found, exiting...\n"
-          "error: wal requires imagemagick to function.")
+    print("Error: ImageMagick wasn't found on your system.",
+          "Try another backend. (wal --backend)")
     sys.exit(1)
 
 

pywal/colors.py

@@ -3,6 +3,7 @@ Generate a palette using various backends.
 """
 import os
 import re
+import shutil
 import sys
 
 from . import backends