BUG: allow graceful recovery for no compiler

If there is no compiler on Linux, the error we were getting was CompileError
rather than the OSError the test was expecting.

This had the nasty side-effect of leaving us in a deleted temporary directory,
causing later test failures.

Try a check to see if we have a compiler and skip otherwise.

numpy/distutils/tests/test_system_info.py

@@ -3,6 +3,8 @@
 import os
 import shutil
 from tempfile import mkstemp, mkdtemp
+from subprocess import Popen, PIPE
+from distutils.errors import DistutilsError
 
 from numpy.distutils import ccompiler
 from numpy.testing import TestCase, run_module_suite, assert_, assert_equal
@@ -54,6 +56,27 @@ def get_class(name, notfound_action=1):
 }
 """
 
+def have_compiler():
+    """ Return True if there appears to be an executable compiler
+    """
+    compiler = ccompiler.new_compiler()
+    try:
+        cmd = compiler.compiler  # Unix compilers
+    except AttributeError:
+        try:
+            compiler.initialize()  # MSVC is different
+        except DistutilsError:
+            return False
+        cmd = [compiler.cc]
+    try:
+        Popen(cmd, stdout=PIPE, stderr=PIPE)
+    except OSError:
+        return False
+    return True
+
+
+HAVE_COMPILER = have_compiler()
+
 
 class test_system_info(system_info):
 
@@ -171,38 +194,39 @@ def test_temp2(self):
         extra = tsi.calc_extra_info()
         assert_equal(extra['extra_link_args'], ['-Wl,-rpath=' + self._lib2])
 
+    @skipif(not HAVE_COMPILER)
     def test_compile1(self):
         # Compile source and link the first source
         c = ccompiler.new_compiler()
+        previousDir = os.getcwd()
         try:
             # Change directory to not screw up directories
-            previousDir = os.getcwd()
             os.chdir(self._dir1)
             c.compile([os.path.basename(self._src1)], output_dir=self._dir1)
             # Ensure that the object exists
             assert_(os.path.isfile(self._src1.replace('.c', '.o')) or
                     os.path.isfile(self._src1.replace('.c', '.obj')))
+        finally:
             os.chdir(previousDir)
-        except OSError:
-            pass
 
+    @skipif(not HAVE_COMPILER)
     @skipif('msvc' in repr(ccompiler.new_compiler()))
     def test_compile2(self):
         # Compile source and link the second source
         tsi = self.c_temp2
         c = ccompiler.new_compiler()
         extra_link_args = tsi.calc_extra_info()['extra_link_args']
+        previousDir = os.getcwd()
         try:
             # Change directory to not screw up directories
-            previousDir = os.getcwd()
             os.chdir(self._dir2)
             c.compile([os.path.basename(self._src2)], output_dir=self._dir2,
                       extra_postargs=extra_link_args)
             # Ensure that the object exists
             assert_(os.path.isfile(self._src2.replace('.c', '.o')))
+        finally:
             os.chdir(previousDir)
-        except OSError:
-            pass
+
 
 if __name__ == '__main__':
     run_module_suite()