Catch FileNotFoundError from Popen and re-raise a more helpful message

galvani/res2sqlite.py

@@ -353,9 +353,16 @@ CREATE VIEW IF NOT EXISTS Capacity_View
 def mdb_get_data_text(s3db, filename, table):
     print("Reading %s..." % table)
     # TODO after dropping Python 2 support - use Popen as contextmanager
-    mdb_sql = sp.Popen(['mdb-export', '-I', 'postgres', filename, table],
-                       bufsize=-1, stdin=None, stdout=sp.PIPE,
-                       universal_newlines=True)
+    try:
+        mdb_sql = sp.Popen(['mdb-export', '-I', 'postgres', filename, table],
+                           bufsize=-1, stdin=None, stdout=sp.PIPE,
+                           universal_newlines=True)
+    except OSError as e:
+        if e.errno == 2:
+            raise RuntimeError('Could not locate the `mdb-export` executable. '
+                               'Check that mdbtools is properly installed.')
+        else:
+            raise
     try:
         # Initialize values to avoid NameError in except clause
         mdb_output = ''
@@ -381,9 +388,16 @@ def mdb_get_data_text(s3db, filename, table):
 def mdb_get_data_numeric(s3db, filename, table):
     print("Reading %s..." % table)
     # TODO after dropping Python 2 support - use Popen as contextmanager
-    mdb_sql = sp.Popen(['mdb-export', filename, table],
-                       bufsize=-1, stdin=None, stdout=sp.PIPE,
-                       universal_newlines=True)
+    try:
+        mdb_sql = sp.Popen(['mdb-export', filename, table],
+                           bufsize=-1, stdin=None, stdout=sp.PIPE,
+                           universal_newlines=True)
+    except OSError as e:
+        if e.errno == 2:
+            raise RuntimeError('Could not locate the `mdb-export` executable. '
+                               'Check that mdbtools is properly installed.')
+        else:
+            raise
     try:
         mdb_csv = csv.reader(mdb_sql.stdout)
         mdb_headers = next(mdb_csv)

tests/test_Arbin.py

@@ -3,7 +3,6 @@
 import os
 import sqlite3
 import subprocess
-import sys
 
 import pytest
 
@@ -28,11 +27,7 @@ def test_convert_Arbin_no_mdbtools(testdata_dir, tmpdir):
     """Checks that the conversion fails with an appropriate error message."""
     res_file = os.path.join(testdata_dir, 'arbin1.res')
     sqlite_file = os.path.join(str(tmpdir), 'arbin1.s3db')
-    if sys.version_info >= (3, 3):
-        expected_exception = FileNotFoundError
-    else:
-        expected_exception = OSError
-    with pytest.raises(expected_exception, match="No such file or directory: 'mdb-export'"):
+    with pytest.raises(RuntimeError, match="Could not locate the `mdb-export` executable."):
         res2sqlite.convert_arbin_to_sqlite(res_file, sqlite_file)