Fix command-not-found handling

Closes #4

bin/grep.py

@@ -0,0 +1,25 @@
+import os
+import re
+import console
+
+def get_app_class(template):
+    class App(template):
+        def F_main(self):
+            pattern = self.argv[1].encode("utf-8")
+            file = self.argv[2]
+
+            try:
+                with open(file, "rb") as f:
+                    for line in f.readlines():
+                        if re.search(pattern, line):
+                            self.console.write(line)
+            except OSError as e:
+                try:
+                    os.listdir(file)
+                    console.write_str(self.console, f"grep: {file}: Is a directory\n")
+                except OSError:
+                    console.write_str(self.console, f"grep: {file}: No such file or directory\n")
+
+            self.exit()
+
+    return App

fibonaccios/apploader.py

@@ -1,3 +1,5 @@
+from fibonaccios.exceptions import *
+
 _cache = {}
 
 def get_app(app):
@@ -6,7 +8,7 @@ def get_app(app):
     except KeyError:
         try:
             module = __import__(f'/bin/{app}')
-        except AttributeError:
+        except ImportError:
             raise AppNotFound(app)
 
         try: