make sqlite open errors clearer

if filesystem permissions on the directory the sqlite database database file is in are such that the app cannot list or create files, sqlite gives a vague error:

```
sqlite3.OperationalError: unable to open database file
```

whereas python's open() will give a better hint ("permission denied"). So, we try opening the database file with python first.

also, add chmods to the startup scripts to avoid this issue in the future

pysonic/database.py

@@ -10,7 +10,7 @@ from collections import Iterable
 from pysonic.scanner import PysonicFilesystemScanner
 
 
-logging = logging.getLogger("database")
+logger = logging.getLogger("database")
 
 
 LETTER_GROUPS = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t",
@@ -63,7 +63,8 @@ class PysonicDatabase(object):
         self.scanner = PysonicFilesystemScanner(self)
 
     def open(self):
-        logging.debug("opening database: %s", self.path)
+        with open(self.path, "rb"):  # sqlite doesn't give very descriptive permission errors, but this does
+            pass
         self.db = sqlite3.connect(self.path, **self.sqlite_opts)
         self.db.row_factory = dict_factory
 
@@ -159,14 +160,14 @@ class PysonicDatabase(object):
 
             # Initialize DB
             if len(c.fetchall()) == 0:
-                logging.warning("Initializing database")
+                logger.warning("Initializing database")
                 for query in queries:
                     c.execute(query)
                 c.execute("COMMIT")
             else:
                 # Migrate if old db exists
                 # c.execute("""UPDATE meta SET value=? WHERE key="db_version";""", (str(version), ))
-                # logging.warning("db schema is version {}".format(version))
+                # logger.warning("db schema is version {}".format(version))
                 pass
 
     def get_artist_info(self, item_id):

start.sh

@@ -1,5 +1,8 @@
 #!/bin/bash
 
-chown -R app:app /db/
+set -x
+
+chmod 755 /db/.
+chown -R app:app /db
 
 exec sudo --preserve-env -Hu app pysonicd $@