Added friendly errors when dependencies are not installed

.travis.yml

@@ -7,7 +7,7 @@ before_install:
   - "sudo apt-get update -qq"
   - "sudo apt-get install python-dev python-pip python-pyexiv2 libimage-exiftool-perl -y"
 install:
-  - "sudo pip install docopt LatLon nose requests"
+  - "sudo pip install docopt LatLon mock nose requests"
 # command to run tests
 # test mapquest key
 before_script:

elodie.py

@@ -7,6 +7,12 @@ import sys
 from datetime import datetime
 from docopt import docopt
 
+# Verify that external dependencies are present first, so the user gets a
+# more user-friendly error instead of an ImportError traceback.
+from elodie.dependencies import verify_dependencies
+if not verify_dependencies():
+    sys.exit(1)
+
 from elodie import constants
 from elodie import geolocation
 from elodie.media.media import Media

elodie/dependencies.py

@@ -0,0 +1,61 @@
+"""Helpers for checking external dependencies."""
+
+import os
+import sys
+from distutils.spawn import find_executable
+
+
+EXIFTOOL_ERROR = u"""
+It looks like you don't have exiftool installed, which Elodie requires.
+Please take a look at the installation steps in the readme:
+
+https://github.com/jmathai/elodie#install-everything-you-need
+""".lstrip()
+
+PYEXIV2_ERROR = u"""
+{error_class_name}: {error}
+
+It looks like you don't have pyexiv2 installed, which Elodie requires for
+geolocation. Please take a look at the installation steps in the readme:
+
+https://github.com/jmathai/elodie#install-everything-you-need
+""".lstrip()
+
+
+def get_exiftool():
+    """Get path to executable exiftool binary.
+
+    We wrap this since we call it in a few places and we do a fallback.
+
+    @returns, None or string
+    """
+    path = find_executable('exiftool')
+    # If exiftool wasn't found we try to brute force the homebrew location
+    if path is None:
+        path = '/usr/local/bin/exiftool'
+        if not os.path.isfile(path) or not os.access(path, os.X_OK):
+            return None
+    return path
+
+
+def verify_dependencies():
+    """Verify that external dependencies are installed.
+
+    Prints a message to stderr and returns False if any dependencies are
+    missing.
+
+    @returns, bool
+    """
+    exiftool = get_exiftool()
+    if exiftool is None:
+        print >>sys.stderr, EXIFTOOL_ERROR
+        return False
+
+    try:
+        import pyexiv2
+    except ImportError as e:
+        print >>sys.stderr, PYEXIV2_ERROR.format(
+            error_class_name=e.__class__.__name__, error=e)
+        return False
+
+    return True

elodie/media/media.py

@@ -4,8 +4,8 @@ Media package that's a parent class for media objects
 """
 
 # load modules
-from distutils.spawn import find_executable
 from elodie import constants
+from elodie.dependencies import get_exiftool
 
 import mimetypes
 import os
@@ -48,22 +48,6 @@ class Media(object):
 
         return exiftool_attributes['album']
 
-    """
-    Get path to executable exiftool binary.
-    We wrap this since we call it in a few places and we do a fallback.
-
-    @returns, None or string
-    """
-    def get_exiftool(self):
-        exiftool = find_executable('exiftool')
-        # If exiftool wasn't found we try to brute force the homebrew location
-        if(exiftool is None):
-            exiftool = '/usr/local/bin/exiftool'
-            if(not os.path.isfile(exiftool) or not os.access(exiftool, os.X_OK)):  # noqa
-                return None
-
-        return exiftool
-
     """
     Get the full path to the video.
 
@@ -103,7 +87,7 @@ class Media(object):
         if(self.exiftool_attributes is not None):
             return self.exiftool_attributes
 
-        exiftool = self.get_exiftool()
+        exiftool = get_exiftool()
         if(exiftool is None):
             return False
 
@@ -222,7 +206,7 @@ class Media(object):
         if(name is None):
             return False
 
-        exiftool = self.get_exiftool()
+        exiftool = get_exiftool()
         if(exiftool is None):
             return False
 

elodie/media/video.py

@@ -16,6 +16,7 @@ import time
 
 from elodie import constants
 from elodie import plist_parser
+from elodie.dependencies import get_exiftool
 from media import Media
 
 
@@ -145,7 +146,7 @@ class Video(Media):
     @returns, string or None if exiftool is not found
     """
     def get_exif(self):
-        exiftool = self.get_exiftool()
+        exiftool = get_exiftool()
         if(exiftool is None):
             return None
 

elodie/tests/dependencies_test.py

@@ -0,0 +1,18 @@
+import mock
+
+from elodie.dependencies import get_exiftool
+
+
+@mock.patch('elodie.dependencies.find_executable')
+@mock.patch('elodie.dependencies.os')
+def test_exiftool(mock_os, mock_find_executable):
+    mock_find_executable.return_value = '/path/to/exiftool'
+    assert get_exiftool() == '/path/to/exiftool'
+
+    mock_find_executable.return_value = None
+    mock_os.path.isfile.return_value = True
+    mock_os.path.access.return_value = True
+    assert get_exiftool() == '/usr/local/bin/exiftool'
+
+    mock_os.path.isfile.return_value = False
+    assert get_exiftool() is None

elodie/tests/media/media_test.py

@@ -21,11 +21,6 @@ from elodie.media.video import Video
 
 os.environ['TZ'] = 'GMT'
 
-def test_exiftool():
-    media = Media()
-    exiftool = media.get_exiftool()
-
-    assert exiftool is not None, exiftool
 
 def test_get_file_path():
     media = Media(helper.get_file('plain.jpg'))