fixing empty lines and comments in apt.txt

repo2docker/buildpacks/base.py

@@ -418,13 +418,19 @@ class BaseImage(BuildPack):
         assemble_scripts = []
         try:
             with open(self.binder_path('apt.txt')) as f:
-                extra_apt_packages = [l.strip() for l in f]
+
+                extra_apt_packages = []
+                for l in f:
+                    package = l.partition('#')[0].strip()
+                    if not package:
+                       continue
                     # Validate that this is, indeed, just a list of packages
                     # We're doing shell injection around here, gotta be careful.
                     # FIXME: Add support for specifying version numbers
-            for p in extra_apt_packages:
-                if not re.match(r"^[a-z0-9.+-]+", p):
-                    raise ValueError("Found invalid package name {} in apt.txt".format(p))
+                    if not re.match(r"^[a-z0-9.+-]+", package):
+                       raise ValueError("Found invalid package name {} in apt.txt".format(package))
+                extra_apt_packages.append(package)
+
 
             assemble_scripts.append((
                 'root',

tests/venv/apt-packages/apt.txt

@@ -1 +1,2 @@
+# testing to skip comments in this file
 gfortran