Simplify prepare_command function and add deprecation warning

cibuildwheel/__main__.py

@@ -1,5 +1,5 @@
 from __future__ import print_function
-import argparse, os, subprocess, sys, textwrap
+import argparse, os, subprocess, sys, textwrap, warnings
 
 import cibuildwheel
 import cibuildwheel.linux, cibuildwheel.windows, cibuildwheel.macos
@@ -25,6 +25,9 @@ def get_option_from_environment(option_name, platform=None):
 
 
 def main():
+    # enable deprecation warnings
+    warnings.filterwarnings("once", ".*", DeprecationWarning)
+
     parser = argparse.ArgumentParser(
         description='Build wheels for all the platforms.',
         epilog=('Most options are supplied via environment variables. '

cibuildwheel/linux.py

@@ -103,10 +103,10 @@ def build(project_dir, package_name, output_dir, test_command, test_requires, be
             pybin_paths=' '.join(c.path+'/bin' for c in platform_configs),
             test_requires=' '.join(test_requires),
             test_command=shlex_quote(
-                prepare_command(test_command, python='python', pip='pip', project='/project') if test_command else ''
+                prepare_command(test_command, project='/project') if test_command else ''
             ),
             before_build=shlex_quote(
-                prepare_command(before_build, python='python', pip='pip', project='/project') if before_build else ''
+                prepare_command(before_build, project='/project') if before_build else ''
             ),
             environment_exports='\n'.join(environment.as_shell_commands()),
         )

cibuildwheel/macos.py

@@ -93,7 +93,7 @@ def build(project_dir, package_name, output_dir, test_command, test_requires, be
 
         # run the before_build command
         if before_build:
-            before_build_prepared = prepare_command(before_build, python=python, pip=pip, project=abs_project_dir)
+            before_build_prepared = prepare_command(before_build, project=abs_project_dir)
             call(before_build_prepared, env=env, shell=True)
 
         # build the wheel
@@ -120,7 +120,7 @@ def build(project_dir, package_name, output_dir, test_command, test_requires, be
             # run the tests from $HOME, with an absolute path in the command
             # (this ensures that Python runs the tests against the installed wheel
             # and not the repo code)
-            test_command_prepared = prepare_command(test_command, python=python, pip=pip, project=abs_project_dir)
+            test_command_prepared = prepare_command(test_command, project=abs_project_dir)
             call(shlex.split(test_command_prepared), cwd=os.environ['HOME'], env=env)
 
         # we're all done here; move it to output

cibuildwheel/util.py

@@ -1,16 +1,21 @@
 from fnmatch import fnmatch
+import warnings
 
 
-def prepare_command(command, python, pip, project):
+def prepare_command(command, project):
     '''
-    Preprocesses a command by expanding variables like {python} or {pip}.
+    Preprocesses a command by expanding variables like {project}.
 
     For example, used for the before_build option, where the user would
     like to run a command like `python setup.py test`. If the command should run on
     Python 3, the user could write `{python} setup.py test`. This command would expand
     it out to python2 or python3 as appropriate.
     '''
-    return command.format(python=python, pip=pip, project=project)
+    if '{python}' in command or '{pip}' in command:
+        warnings.warn("'{python}' and '{pip}' are no longer needed, and have been deprecated. Simply use 'python' or 'pip' instead.",
+            DeprecationWarning)
+
+    return command.format(python='python', pip='pip', project=project)
 
 
 class BuildSkipper(object):

cibuildwheel/windows.py

@@ -78,7 +78,7 @@ def build(project_dir, package_name, output_dir, test_command, test_requires, be
 
         # run the before_build command
         if before_build:
-            before_build_prepared = prepare_command(before_build, python='python', pip='pip', project=abs_project_dir)
+            before_build_prepared = prepare_command(before_build, project=abs_project_dir)
             shell([before_build_prepared], env=env)
 
         # build the wheel
@@ -95,7 +95,7 @@ def build(project_dir, package_name, output_dir, test_command, test_requires, be
             # run the tests from c:\, with an absolute path in the command
             # (this ensures that Python runs the tests against the installed wheel
             # and not the repo code)
-            test_command_prepared = prepare_command(test_command, python='python', pip='pip', project=abs_project_dir)
+            test_command_prepared = prepare_command(test_command, project=abs_project_dir)
             shell([test_command_prepared], cwd='c:\\', env=env)
 
         # we're all done here; move it to output