Rename, add docstrings and close file

Author: GeorgianaElena

repo2docker/buildpacks/repo2docker-entrypoint

@@ -45,7 +45,7 @@ def main():
             break
     # raise Exception if log_file could not be set
     if log_file is None:
-        raise Exception("Could not open '.jupyter-server-log.txt' log file " )
+        raise Exception("Could not open '.jupyter-server-log.txt' log file")
 
     # build the command
     # like `exec "$@"`
@@ -74,23 +74,27 @@ def main():
     for signum in SIGNALS:
         signal.signal(signum, relay_signal)
 
-    enospc = {
-        sys.stdout.buffer: False,
-        log_file: False
+    # keep a record of the output streams that ran out space
+    writable = {
+        sys.stdout.buffer: True,
+        log_file: True
     }
 
     # tee output from child to both our stdout and the log file
     def tee(chunk):
-        """Tee output from child to the log file"""
+        """Tee output from child to both our stdout and the log file"""
         for f in [sys.stdout.buffer, log_file]:
-            if not enospc[f]:
+            if writable[f]:
                 try:
                     f.write(chunk)
                     f.flush()
                 except OSError as e:
                     if e.errno == errno.ENOSPC:
-                        enospc[f] = True
+                        # mark the stream as not writable anymore
+                        writable[f] = False
                         continue
+                    else:
+                        raise
 
     # make stdout pipe non-blocking
     # this means child.stdout.read(nbytes)
@@ -118,6 +122,8 @@ def main():
         tee(chunk)
         chunk = child.stdout.read()
 
+    log_file.close()
+
     # make our returncode match the child's returncode
     sys.exit(child.returncode)